Customizable titration for an implantable neurostimulator

ABSTRACT

Systems and methods for customizable titration of an implantable neurostimulator are provided. A method of titrating a neurostimulation signal delivered to a patient from an implantable pulse generator includes delivering a first neurostimulation signal with a first set of parameters, increasing a first value of the first neurostimulation signal at a first rate for a first period of time while delivering the first neurostimulation signal, ceasing delivery of the first neurostimulation signal when the first value reaches a first target value, delivering a second neurostimulation signal with a second set of parameters, and increasing the second neurostimulation signal at a second rate for a second period of time while delivering the second neurostimulation signal.

CROSS-REFERENCE TO RELTED APPLICATIONS

This application is a continuation of International Application No. PCT/US2018/050930 filed Sep. 13, 2018, which claims the benefit of and priority to U.S. Provisional Patent Application No. 62/558,817, filed Sep. 14, 2017, the disclosures of both of which are incorporated by reference herein in their entirety.

BACKGROUND

The present disclosure relates generally to neurostimulation and, more specifically, to improved systems and methods for managing titration of stimulation.

Chronic heart failure (CHF) and other forms of chronic cardiac dysfunction (CCD) may be related to an autonomic imbalance of the sympathetic and parasympathetic nervous systems that, if left untreated, can lead to cardiac arrhythmogenesis, progressively worsening cardiac function, and eventual patient death. CHF is pathologically characterized by an elevated neuroexitatory state and is accompanied by physiological indications of impaired arterial and cardiopulmonary baroreflex function with reduced vagal activity.

CHF triggers compensatory activations of the sympathoadrenal (sympathetic) nervous system and the renin-angiotensin-aldosterone hormonal system, which initially helps to compensate for deteriorating heart-pumping function, yet, over time, can promote progressive left ventricular dysfunction and deleterious cardiac remodeling. Patients suffering from CHF are at increased risk of tachyarrhythmias, such as atrial fibrillation (AF), ventricular tachyarrhythmias (ventricular tachycardia (VT) and ventricular fibrillation (VF)), and atrial flutter, particularly when the underlying morbidity is a form of coronary artery disease, cardiomyopathy, mitral valve prolapse, or other valvular heart disease. Sympathoadrenal activation also significantly increases the risk and severity of tachyarrhythmias due to neuronal action of the sympathetic nerve fibers in, on, or around the heart and through the release of epinephrine (adrenaline), which can exacerbate an already-elevated heart rate.

The standard of care for managing CCD in general continues to evolve. For instance, new therapeutic approaches that employ electrical stimulation of neural structures that directly address the underlying cardiac autonomic nervous system imbalance and dysregulation have been proposed. In one form, controlled stimulation of the cervical vagus nerve beneficially modulates cardiovascular regulatory function. Vagus nerve stimulation (VNS) has been used for the clinical treatment of drug-refractory epilepsy and depression, and more recently has been proposed as a therapeutic treatment of heart conditions such as CHF.

VNS therapy commonly requires implantation of a neurostimulator, a surgical procedure requiring several weeks of recovery before the neurostimulator can be activated and a patient can start receiving VNS therapy. Even after the recovery and activation of the neurostimulator, a full therapeutic dose of VNS is not immediately delivered to the patient to avoid causing significant patient discomfort and other undesirable side effects. Instead, to allow the patient to adjust to the VNS therapy, a titration process is utilized in which the intensity is gradually increased over a period of time under a control of a physician, with the patient given time between successive increases in VNS therapy intensity to adapt to the new intensity. As stimulation is chronically applied at each new intensity level, the patient's tolerance threshold, or tolerance zone boundary, gradually increases, allowing for an increase in intensity during subsequent titration sessions. The titration process can take significantly longer in practice because the increase in intensity is generally performed by a physician or other healthcare provider, and thus, for every step in the titration process to take place, the patient has to visit the provider's office to have the titration adjustments performed. Scheduling conflicts in the provider's office may increase the time between titration sessions, thereby extending the overall titration process, during which the patient in need of VNS does not receive the VNS at the full therapeutic intensity.

For patients receiving VNS therapy for the treatment of epilepsy, a titration process that continues over an extended period of time, such as six to twelve months, may be somewhat acceptable because the patient's health condition typically would not worsen in that period of time. However, for patients being treated for other health conditions, such as CHF, the patient's condition may degrade rapidly if left untreated. As a result, there is a much greater urgency to completing the VNS titration process when treating a patient with a time-sensitive condition, such as CHF.

Accordingly, a need remains for an approach to efficiently titrate neurostimulation therapy for treating chronic cardiac dysfunction and other conditions while minimizing side effects and related discomfort caused by the titration or by the VNS therapy itself.

SUMMARY

One embodiment relates to a method of titrating a neurostimulation signal delivered to a patient from an implantable pulse generator. The method includes delivering a first neurostimulation signal with a first set of parameters, the first set of parameters having a first value for at least one of output current, frequency, pulse width, or duty cycle;increasing the first value of the first neurostimulation signal at a first rate for a first period of time while delivering the first neurostimulation signal; and ceasing delivery of the first neurostimulation signal when the first value reaches a first target value. The method further includes delivering a second neurostimulation signal with a second set of parameters, the second set of parameters having a second value for at least one of output current, frequency, pulse width, or duty cycle, the second value being equal to the first target value, and increasing the second neurostimulation signal at a second rate for a second period of time while delivering the second neurostimulation signal, the second rate being different than the first rate.

Another embodiment relates to a neurostimulation system. The neurostimulation system includes an implantable medical device (IMD) including a neurostimulator coupled to an electrode assembly, the neurostimulator adapted to deliver a neurostimulation signal to a patient. The neurostimulation system also includes a control system. The control system is programmed to deliver a first neurostimulation signal with a first set of parameters, the first set of parameters having a first value for at least one of output current, frequency, pulse width, or duty cycle; increase the first value of the first neurostimulation signal at a first rate for a first period of time while delivering the first neurostimulation signal; and cease delivery of the first neurostimulation signal when the first value reaches a first target value. The control system is further programmed to deliver a second neurostimulation signal with a second set of parameters, the second set of parameters having a second value for at least one of output current, frequency, pulse width, or duty cycle, the second value being equal to the first target value, and increase the second neurostimulation signal at a second rate for a second period of time while delivering the second neurostimulation signal, the second rate being different than the first rate.

Another embodiment relates to a non-transitory computer-readable medium including instructions executable by a processor. The instructions are executable by the processor to deliver a first neurostimulation signal with a first set of parameters, the first set of parameters having a first value for at least one of output current, frequency, pulse width, or duty cycle; increase the first value of the first neurostimulation signal at a first rate for a first period of time while delivering the first neurostimulation signal; and cease delivery of the first neurostimulation signal when the first value reaches a first target value. The instructions are further executable by the processor to deliver a second neurostimulation signal with a second set of parameters, the second set of parameters having a second value for at least one of output current, frequency, pulse width, or duty cycle, the second value being equal to the first target value, and increase the second neurostimulation signal at a second rate for a second period of time while delivering the second neurostimulation signal, the second rate being different than the first rate.

Another embodiment relates to a method of titrating a neurostimulation signal delivered to a patient from an implantable pulse generator. The method includes delivering the neurostimulation signal in conformance with a first titration aggressiveness profile, the first titration aggressiveness profile having a first set of parameters having a first value for at least one of output current, frequency, pulse width, or duty cycle; increasing the first value for the at least one of output current, frequency, pulse width, or duty cycle towards a target value; and receiving a feedback signal from the patient indicating adverse effects from the neurostimulation signal. The method also includes, in response to receiving the feedback signal, modifying the neurostimulation signal to conform with a second titration aggressiveness profile, the second aggressiveness profile having a second set of parameters having a second value for at least one of output current, frequency, pulse width, or duty cycle, delivering the neurostimulation signal with the second titration aggressiveness profile, and increasing the second value for the at least one of output current, frequency, pulse width, or duty cycle towards the target value.

Another embodiment relates to a neurostimulation system. The neurostimulation system includes an implantable medical device (IMD) including a neurostimulator coupled to an electrode assembly, the neurostimulator adapted to deliver a neurostimulation signal to a patient. The neurostimulation system also includes a control system. The control system is programmed to deliver the neurostimulation signal in conformance with a first titration aggressiveness profile, the first titration aggressiveness profile having a first set of parameters having a first value for at least one of output current, frequency, pulse width, or duty cycle; increase the first value for the at least one of output current, frequency, pulse width, or duty cycle towards a target value; and receive a feedback signal from the patient indicating adverse effects from the neurostimulation signal. The control system is also programmed to, in response to receiving the feedback signal, modify the neurostimulation signal to conform with a second titration aggressiveness profile, the second aggressiveness profile having a second set of parameters having a second value for at least one of output current, frequency, pulse width, or duty cycle, deliver the neurostimulation signal with the second titration aggressiveness profile, and increase the second value for the at least one of output current, frequency, pulse width, or duty cycle towards the target value.

Another embodiment relates to a non-transitory computer-readable medium including instructions executable by a processor. The instructions are executable by the processor to deliver the neurostimulation signal in conformance with a first titration aggressiveness profile, the first titration aggressiveness profile having a first set of parameters having a first value for at least one of output current, frequency, pulse width, or duty cycle; increase the first value for the at least one of output current, frequency, pulse width, or duty cycle towards a target value; and receive a feedback signal from the patient indicating adverse effects from the neurostimulation signal. The instructions are also executable by the processor to, in response to receiving the feedback signal, modify the neurostimulation signal to conform with a second titration aggressiveness profile, the second aggressiveness profile having a second set of parameters having a second value for at least one of output current, frequency, pulse width, or duty cycle, deliver the neurostimulation signal with the second titration aggressiveness profile, and increase the second value for the at least one of output current, frequency, pulse width, or duty cycle towards the target value.

Another embodiment relates to a programmer configured to communicate with an implantable pulse generator that provides neurostimulation. The programmer includes communication circuitry, a user interface, a processor, and a memory. The memory has instructions stored thereon that, when executed by the processor, cause the processor to collect, via the communication circuitry, data about ongoing neurostimulation being applied by the implantable pulse generator while in communication with the communication circuitry and display, via the user interface, an indication relating to a timing of neurostimulation bursts applied by the implantable pulse generator while in communication with the communication circuitry based on the collected data.

Another embodiment relates to a method of displaying, by a programmer configured to communicate with an implantable pulse generator, an indication of active neurostimulation applied by the implantable pulse generator. The method includes collecting data about ongoing neurostimulation being applied by the implantable pulse generator while in communication with the programmer and displaying an indication relating to a timing of neurostimulation bursts applied by the implantable pulse generator while in communication with the programmer based on the collected data.

Another embodiment relates to a non-transitory computer-readable medium for a programmer including instructions executable by a processor. The instructions are executable by the processor to collect data from an implantable pulse generator about ongoing neurostimulation being applied by the implantable pulse generator while in communication with the programmer and display, via a user interface, an indication relating to a timing of neurostimulation bursts applied by the implantable pulse generator while in communication with the programmer based on the collected data.

Another embodiment relates to a method of titrating a neurostimulation signal delivered to a patient from an implantable pulse generator. The method includes delivering the neurostimulation signal in conformance with a first set of parameters, the first set of parameters having a first value for at least one of output current, frequency, pulse width, or duty cycle, and receiving a first indicator, the indicator being associated with at least one of a titration hold time or a titration hold duration. The method also includes initiating a titration hold of the titrating of the neurostimulation signal in response to the first indicator, the titration hold corresponding to the continuation of the neurostimulation signal conforming with the first set of parameters, and receiving a second indicator, the second indicator associated with at least one of a titration resumption time or a completion of the titration hold duration. The method further includes resuming the titrating of the neurostimulation signal in response to the second indicator. The titration hold is a temporary hold configured to reduce adverse effects observed by the patient during the titrating.

Another embodiment relates to a neurostimulation system. The neurostimulation system includes an implantable medical device (IMD) including a neurostimulator coupled to an electrode assembly, the neurostimulator adapted to deliver a neurostimulation signal to a patient. The neurostimulation system also includes a control system. The control system is programmed to deliver the neurostimulation signal in conformance with a first set of parameters, the first set of parameters having a first value for at least one of output current, frequency, pulse width, or duty cycle, and receive a first indicator, the indicator being associated with at least one of a titration hold time or a titration hold duration. The control system is also programmed to initiate a titration hold of the titrating of the neurostimulation signal in response to the first indicator, the titration hold corresponding to the continuation of the neurostimulation signal conforming with the first set of parameters, and receive a second indicator, the second indicator associated with at least one of a titration resumption time or a completion of the titration hold duration. The control system is further programmed to resume the titrating of the neurostimulation signal in response to the second indicator. The titration hold is a temporary hold configured to reduce adverse effects observed by the patient during the titrating.

Another embodiment relates to a non-transitory computer-readable medium including instructions executable by a processor. The instructions are executable by the processor to deliver the neurostimulation signal in conformance with a first set of parameters, the first set of parameters having a first value for at least one of output current, frequency, pulse width, or duty cycle, and receive a first indicator, the indicator being associated with at least one of a titration hold time or a titration hold duration. The instructions are also executable by the processor to initiate a titration hold of the titrating of the neurostimulation signal in response to the first indicator, the titration hold corresponding to the continuation of the neurostimulation signal conforming with the first set of parameters, and receive a second indicator, the second indicator associated with at least one of a titration resumption time or a completion of the titration hold duration. The instructions are further executable by the processor to resume the titrating of the neurostimulation signal in response to the second indicator. The titration hold is a temporary hold configured to reduce adverse effects observed by the patient during the titrating.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, characteristics, and advantages of the present disclosure will become apparent to a person of ordinary skill in the art from the following detailed description of embodiments of the present disclosure, made with reference to the drawings annexed, in which like reference characters refer to like elements.

FIG. 1 is a front anatomical diagram showing, by way of example, placement of an implantable vagus stimulation device in a male patient, in accordance with one embodiment.

FIGS. 2A and 2B are diagrams respectively showing the implantable neurostimulator and the stimulation therapy lead of FIG. 1, according to an exemplary embodiment.

FIG. 3 is a diagram showing an external programmer for use with the implantable neurostimulator of FIG. 1, according to an exemplary embodiment.

FIG. 4 is a diagram showing electrodes provided as on the stimulation therapy lead of FIG. 2 in place on a vagus nerve in situ, according to an exemplary embodiment.

FIG. 5 is a flowchart of a method for delivering vagus nerve stimulation therapy, according to an exemplary embodiment.

FIGS. 6A and 6B are flowcharts of a titration process, according to an exemplary embodiment.

FIGS. 7A and 7B are block diagrams of neurostimulation systems, according to an exemplary embodiment.

FIG. 8 is a titration assist management dashboard, according to an exemplary embodiment.

FIG. 9 is a patient titration graph of the titration assist management dashboard of FIG. 8, according to an exemplary embodiment.

FIG. 10 is a flowchart of a process for managing patients using the titration assist management dashboard, according to an exemplary embodiment.

FIG. 11 is a patient titration graph incorporating a titration dwell point, according to an exemplary embodiment.

FIG. 12 is a flowchart of a titration process incorporating a titration dwell point, according to an exemplary embodiment.

FIG. 13 is a patient titration graph illustrating different titration aggressiveness profiles, according to an exemplary embodiment.

FIG. 14 is a flowchart of a titration process including different titration aggressiveness profiles, according to an exemplary embodiment.

FIG. 15 is a flowchart of process of displaying an indication of active neurostimulation, according to an exemplary embodiment.

FIG. 16 is a patient titration graph incorporating a titration black-out period, according to an exemplary embodiment.

FIG. 17 is a flowchart of a titration process incorporating a titration black-out period, according to an exemplary embodiment.

DETAILED DESCRIPTION

Various aspects of the disclosure will now be described with regard to certain examples and embodiments, which are intended to illustrate but not to limit the disclosure. Nothing in this disclosure is intended to imply that any particular feature or characteristic of the disclosed embodiments is essential. The scope of protection is defined by the claims that follow this description and not by any particular embodiment described herein. Before turning to the figures, which illustrate example embodiments in detail, it should be understood that the application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.

CHF and other cardiovascular diseases cause derangement of autonomic control of the cardiovascular system, favoring increased sympathetic and decreased parasympathetic central outflow. These changes are accompanied by elevation of basal heart rate arising from chronic sympathetic hyperactivation along the neurocardiac axis.

The vagus nerve is a diverse nerve trunk that contains both sympathetic and parasympathetic fibers and both afferent and efferent fibers. These fibers have different diameters and myelination and subsequently have different activation thresholds. This results in a graded response as intensity is increased. Low intensity stimulation results in a progressively greater tachycardia, which then diminishes and is replaced with a progressively greater bradycardia response as intensity is further increased. Peripheral neurostimulation therapies that target the fluctuations of the autonomic nervous system have been shown to improve clinical outcomes in some patients. Specifically, autonomic regulation therapy results in simultaneous creation and propagation of efferent and afferent action potentials within nerve fibers comprising the cervical vagus nerve. The therapy directly improves autonomic balance by engaging both medullary and cardiovascular reflex control components of the autonomic nervous system. Upon stimulation of the cervical vagus nerve, action potentials propagate away from the stimulation site in two directions, efferently toward the heart and afferently toward the brain. Efferent action potentials influence the intrinsic cardiac nervous system and the heart and other organ systems, while afferent action potentials influence central elements of the nervous system.

An implantable vagus nerve stimulator, such as used to treat drug-refractory epilepsy and depression, can be adapted for use in managing chronic cardiac dysfunction (CCD) through therapeutic bi-directional vagus nerve stimulation. FIG. 1 is a front anatomical diagram showing, by way of example, placement of an implantable medical device (e.g., a vagus nerve stimulation (VNS) system 11, as shown in FIG. 1) in a male patient 10, according to an exemplary embodiment. The VNS provided through the stimulation system 11 operates under several mechanisms of action. These mechanisms include increasing parasympathetic outflow and inhibiting sympathetic effects by inhibiting norepinephrine release and adrenergic receptor activation. More importantly, VNS triggers the release of the endogenous neurotransmitter acetylcholine and other peptidergic substances into the synaptic cleft, which has several beneficial anti-arrhythmic, anti-apoptotic, and anti-inflammatory effects as well as beneficial effects at the level of the central nervous system.

The implantable vagus stimulation system 11 comprises an implantable neurostimulator or pulse generator 12 and a stimulating nerve electrode assembly 125. The neurostimulator or pulse generator may be a voltage stimulator or, more preferably, a current stimulator. The stimulating nerve electrode assembly 125, comprising at least an electrode pair, is conductively connected to the distal end of an insulated, electrically conductive lead assembly 13 and electrodes 14. The electrodes 14 may be provided in a variety of forms, such as, e.g., helical electrodes, probe electrodes, cuff electrodes, as well as other types of electrodes.

The implantable vagus stimulation system 11 can be remotely accessed following implant through an external programmer, such as the programmer 40 shown in FIG. 3 and described in further detail below. The programmer 40 can be used by healthcare professionals to check and program the neurostimulator 12 after implantation in the patient 10 and to adjust stimulation parameters during the stimulation titration process. In some embodiments, an external magnet may provide basic controls. For example, an electromagnetic controller may enable the patient 10 or healthcare professional to interact with the implanted neurostimulator 12 to exercise increased control over therapy delivery and suspension. For further example, an external programmer may communicate with the neurostimulation system 11 via other wired or wireless communication methods, such as, e.g., wireless RF transmission. Together, the implantable vagus stimulation system 11 and one or more of the external components form a VNS therapeutic delivery system.

The neurostimulator 12 is typically implanted in the patient's right or left pectoral region generally on the same side (ipsilateral) as the vagus nerve 15, 16 to be stimulated, although other neurostimulator-vagus nerve configurations, including contra-lateral and bi-lateral are possible. A vagus nerve typically comprises two branches that extend from the brain stem respectively down the left side and right side of the patient, as seen in FIG. 1. The electrodes 14 are generally implanted on the vagus nerve 15, 16 about halfway between the clavicle 19 a-b and the mastoid process. The electrodes may be implanted on either the left or right side. The lead assembly 13 and electrodes 14 are implanted by first exposing the carotid sheath and chosen branch of the vagus nerve 15, 16 through a latero-cervical incision (perpendicular to the long axis of the spine) on the ipsilateral side of the patient's neck 18. The helical electrodes 14 are then placed onto the exposed nerve sheath and tethered. A subcutaneous tunnel is formed between the respective implantation sites of the neurostimulator 12 and helical electrodes 14, through which the lead assembly 13 is guided to the neurostimulator 12 and securely connected. Additionally, in various embodiments, the neurostimulator 12 connects to the electrodes 14 as shown in FIG. 4 (e.g., at the top helices).

In one embodiment, the neural stimulation is provided as a low level maintenance dose independent of cardiac cycle. The stimulation system 11 bi-directionally stimulates either the left vagus nerve 15 or the right vagus nerve 16. However, it is contemplated that multiple electrodes 14 and multiple leads 13 could be utilized to stimulate simultaneously, alternatively, or in other various combinations. Stimulation may be through multimodal application of continuously-cycling, intermittent and periodic electrical stimuli, which are parametrically defined through stored stimulation parameters and timing cycles. Both sympathetic and parasympathetic nerve fibers in the vagosympathetic complex are stimulated. Generally, cervical vagus nerve stimulation results in propagation of action potentials from the site of stimulation in a bi-directional manner. The application of bi-directional propagation in both afferent and efferent directions of action potentials within neuronal fibers comprising the cervical vagus nerve improves cardiac autonomic balance. Afferent action potentials propagate toward the parasympathetic nervous system's origin in the medulla in the nucleus ambiguus, nucleus tractus solitarius, and the dorsal motor nucleus, as well as towards the sympathetic nervous system's origin in the intermediolateral cell column of the spinal cord. Efferent action potentials propagate toward the heart 17 to activate the components of the heart's intrinsic nervous system. Either the left or right vagus nerve 15, 16 can be stimulated by the stimulation system 11. The right vagus nerve 16 has a moderately lower (approximately 30%) stimulation threshold than the left vagus nerve 15 for heart rate effects at the same stimulation frequency and pulse width.

The VNS therapy is delivered autonomously to the patient's vagus nerve 15, 16 through three implanted components that include a neurostimulator 12, lead assembly 13, and electrodes 14. FIGS. 2A and 2B are diagrams respectively showing the implantable neurostimulator 12 and the stimulation lead assembly 13 of FIG. 1. In one embodiment, the neurostimulator 12 can be adapted from a VNS Therapy Demipulse Model 103 or AspireSR Model 106 pulse generator, manufactured and sold by Cyberonics, Inc., Houston, Tex., although other manufactures and types of implantable VNS neurostimulators could also be used. The stimulation lead assembly 13 and electrodes 14 are generally fabricated as a combined assembly and can be adapted from a Model 302 lead, PerenniaDURA Model 303 lead, or PerenniaFLEX Model 304 lead, also manufactured and sold by Cyberonics, Inc., in three sizes based, for example, on a helical electrode inner diameter, although other manufactures and types of single-pin receptacle-compatible therapy leads and electrodes could also be used.

Referring first to FIG. 2A, the system 20 may be configured to provide multimodal vagus nerve stimulation. In a maintenance mode, the neurostimulator 12 is parametrically programmed to deliver continuously-cycling, intermittent and periodic ON-OFF cycles of VNS. Such delivery produces action potentials in the underlying nerves that propagate bi-directionally, both afferently and efferently.

The neurostimulator 12 includes an electrical pulse generator that is tuned to improve autonomic regulatory function by triggering action potentials that propagate both afferently and efferently within the vagus nerve 15, 16. The neurostimulator 12 is enclosed in a hermetically sealed housing 21 constructed of a biocompatible material, such as titanium. The housing 21 contains electronic circuitry 22 powered by a battery 23, such as a lithium carbon monofluoride primary battery or a rechargeable secondary cell battery. The electronic circuitry 22 may be implemented using complementary metal oxide semiconductor integrated circuits that include a microprocessor controller that executes a control program according to stored stimulation parameters and timing cycles; a voltage regulator that regulates system power; logic and control circuitry, including a recordable memory 29 within which the stimulation parameters are stored, that controls overall pulse generator function, receives and implements programming commands from the external programmer, or other external source, collects and stores telemetry information, processes sensory input, and controls scheduled and sensory-based therapy outputs; a transceiver that remotely communicates with the external programmer using radio frequency signals; an antenna, which receives programming instructions and transmits the telemetry information to the external programmer; and a reed switch 30 that provides remote access to the operation of the neurostimulator 12 using an external programmer, a simple patient magnet, or an electromagnetic controller. The recordable memory 29 can include both volatile (dynamic) and non-volatile/persistent (static) forms of memory, within which the stimulation parameters and timing cycles can be stored. Other electronic circuitry and components are possible.

The neurostimulator 12 includes a header 24 to securely receive and connect to the lead assembly 13. In one embodiment, the header 24 encloses a receptacle 25 into which a single pin for the lead assembly 13 can be received, although two or more receptacles could also be provided, along with the corresponding electronic circuitry 22. The header 24 may internally include a lead connector block (not shown), a setscrew, and a spring contact (not shown) that electrically connects to the lead ring, thus completing an electrical circuit.

In some embodiments, the housing 21 may also contain a heart rate sensor 31 that is electrically interfaced with the logic and control circuitry, which receives the patient's sensed heart rate as sensory inputs. The heart rate sensor 31 monitors heart rate using an ECG-type electrode. Through the electrode, the patient's heartbeat can be sensed by detecting ventricular depolarization. In a further embodiment, a plurality of electrodes can be used to sense voltage differentials between electrode pairs, which can undergo signal processing for cardiac physiological measures, for instance, detection of the P-wave, QRS complex, and T-wave. The heart rate sensor 31 provides the sensed heart rate to the control and logic circuitry as sensory inputs that can be used to determine the onset or presence of arrhythmias, particularly VT, and/or to monitor and record changes in the patient's heart rate over time or in response to applied stimulation signals.

Referring next to FIG. 2B, the lead assembly 13 delivers an electrical signal from the neurostimulator 12 to the vagus nerve 15, 16 via the electrodes 14. On a proximal end, the lead assembly 13 has a lead connector 27 that transitions an insulated electrical lead body to a metal connector pin 28 with a metal connector ring. During implantation, the connector pin 28 is guided through the receptacle 25 into the header 24 and securely fastened in place using the setscrew (not shown) to electrically couple one electrode of the lead assembly 13 to the neurostimulator 12 while a spring contact (not shown) makes electrical contact to the ring connected to the other electrode. On a distal end, the lead assembly 13 terminates with the electrode 14, which bifurcates into a pair of anodic and cathodic electrodes 62 (as further described infra with reference to FIG. 4). In one embodiment, the lead connector 27 is manufactured using silicone, and the connector pin 28 and ring are made of stainless steel, although other suitable materials could be used, as well. The insulated lead body of the lead assembly 13 utilizes a silicone-insulated alloy conductor material.

In some embodiments, the electrodes 14 are helical and placed around the cervical vagus nerve 15, 16 at the location below where the superior and inferior cardiac branches separate from the cervical vagus nerve. In alternative embodiments, the helical electrodes may be placed at a location above where one or both of the superior and inferior cardiac branches separate from the cervical vagus nerve. In one embodiment, the helical electrodes 14 are positioned around the patient's vagus nerve oriented with the end of the helical electrodes 14 facing the patient's head. In an alternate embodiment, the helical electrodes 14 are positioned around the patient's vagus nerve 15, 16 oriented with the end of the helical electrodes 14 facing the patient's heart 17. At the distal end, the insulated electrical lead body of the lead assembly 13 is bifurcated into a pair of lead bodies that are connected to a pair of electrodes. The polarity of the electrodes could be configured into a proximal anode and a distal cathode, or a proximal cathode and a distal anode.

The neurostimulator 12 may be interrogated prior to implantation and throughout the therapeutic period with a healthcare provider-operable control system comprising an external programmer and programming wand (shown in FIG. 3) for checking proper operation, downloading recorded data, diagnosing problems, and programming operational parameters. FIG. 3 is a diagram showing an external programmer 40 for use with the implantable neurostimulator 12 of FIG. 1. The external programmer 40 includes a healthcare provider operable programming computer 41 and a programming wand 42. Generally, use of the external programmer is restricted to healthcare providers, while more limited manual control is provided to the patient through “magnet mode.”

In one embodiment, the external programmer 40 executes application software 45 specifically designed to interrogate the neurostimulator 12. The programming computer 41 interfaces to the programming wand 42 through a wired or wireless data connection. The programming wand 42 can be adapted from a Model 201 Programming Wand, manufactured and sold by Cyberonics, Inc., and the application software 45 can be adapted from the Model 250 Programming Software suite, licensed by Cyberonics, Inc. Other configurations and combinations of external programmer 40, programming wand 42, and application software 45 are possible.

The programming computer 41 can be implemented using a general purpose programmable computer and can be a personal computer, laptop computer, ultrabook computer, netbook computer, handheld computer, tablet computer, smart phone, or other form of computational device. For example, in one embodiment, the programming computer 41 is a tablet programmer with a wired or wireless data connection to the programming wand 42. The programming computer 41 functions through those components conventionally found in such devices, including, for instance, a central processing unit, volatile and persistent memory, touch-sensitive display, control buttons, peripheral input and output ports, and network interface. The computer 41 operates under the control of the application software 45, which is executed as program code as a series of process or method modules or steps by the programmed computer hardware. Other assemblages or configurations of computer hardware, firmware, and software are possible.

Operationally, the programming computer 41, when connected to a neurostimulator 12 through wireless telemetry using the programming wand 42, can be used by a healthcare provider to remotely interrogate the neurostimulator 12 and modify stored stimulation parameters. The programming wand 42 provides data conversion between the digital data accepted by and output from the programming computer and the radio frequency signal format that is required for communication with the neurostimulator 12. In other embodiments, the programming computer may communicate with the implanted neurostimulator 12 using other wireless communication methods, such as wireless RF transmission. The programming computer 41 may further be configured to receive inputs, such as physiological signals received from patient sensors (e.g., implanted or external). These sensors may be configured to monitor one or more physiological signals, e.g., vital signs, such as body temperature, pulse rate, respiration rate, blood pressure, etc. These sensors may be coupled directly to the programming computer 41 or may be coupled to another instrument or computing device which receives the sensor input and transmits the input to the programming computer 41. The programming computer 41 may monitor, record, and/or respond to the physiological signals in order to effectuate stimulation delivery in accordance with some embodiments.

The healthcare provider operates the programming computer 41 through a user interface that includes a set of input controls 43 (e.g., including a touchscreen of the programming computer 41) and a visual display 44, which could be touch-sensitive, upon which to monitor progress, view downloaded telemetry and recorded physiology, and review and modify programmable stimulation parameters. The telemetry can include reports on device history that provide patient identifier, implant date, model number, serial number, magnet activations, total ON time, total operating time, manufacturing date, and device settings and stimulation statistics, and on device diagnostics that include patient identifier, model identifier, serial number, firmware build number, implant date, communication status, output current status, measured current delivered, lead impedance, and battery status. Other kinds of telemetry or telemetry reports are possible.

During interrogation, the programming wand 42 is held by its handle 46 and the bottom surface 47 of the programming wand 42 is placed on the patient's chest over the location of the implanted neurostimulator 12. A set of indicator lights 49 can assist with proper positioning of the wand and a set of input controls 48 enable the programming wand 42 to be operated directly, rather than requiring the healthcare provider to awkwardly coordinate physical wand manipulation with control inputs via the programming computer 41. The sending of programming instructions and receipt of telemetry information occur wirelessly through radio frequency signal interfacing. Other programming computer and programming wand operations are possible.

FIG. 4 is a diagram showing the helical electrodes 14 provided as on the stimulation lead assembly 13 of FIG. 2 in place on a vagus nerve 15, 16 in situ 50. Although described with reference to a specific manner and orientation of implantation, the specific surgical approach and implantation site selection particulars may vary, depending upon physician discretion and patient physical structure.

Under one embodiment, helical electrodes 14 may be positioned on the patient's vagus nerve 61 oriented with the end of the helical electrodes 14 facing the patient's head. At the distal end, the insulated electrical lead body of the lead assembly 13 is bifurcated into a pair of lead bodies 57, 58 that are connected to a pair of electrodes 51, 52. The polarity of the electrodes 51, 52 could be configured into a proximal anode and a distal cathode, or a proximal cathode and a distal anode. In addition, an anchor tether 53 is fastened over or in connection with the lead bodies 57, 58 that maintains the helical electrodes' position on the vagus nerve 61 following implant. In one embodiment, the conductors of the electrodes 51, 52 are manufactured using a platinum and iridium alloy, while the helical materials of the electrodes 51, 52 and the anchor tether 53 are a silicone elastomer.

During surgery, the electrodes 51, 52 and the anchor tether 53 are coiled around the vagus nerve 61 proximal to the patient's head, each with the assistance of a pair of sutures 54, 55, 56, made of polyester or other suitable material, which help the surgeon to spread apart the respective helices. The lead bodies 57, 58 of the electrodes 51, 52 are oriented distal to the patient's head and aligned parallel to each other and to the vagus nerve 61. A strain relief bend 60 can be formed on the distal end with the insulated electrical lead body of the lead assembly 13 aligned, for example, parallel to the helical electrodes 14 and attached to the adjacent fascia by a plurality of tie-downs 59 a-b.

The neurostimulator 12 delivers VNS under control of the electronic circuitry 22. The stored stimulation parameters are programmable. Each stimulation parameter can be independently programmed to define the characteristics of the cycles of therapeutic stimulation and inhibition to ensure optimal stimulation for a patient 10. The programmable stimulation parameters include output current, signal frequency, pulse width, signal ON time, signal OFF time, magnet activation (for VNS specifically triggered by “magnet mode”), and reset parameters. Other programmable parameters are possible. In addition, sets or “profiles” of preselected stimulation parameters can be provided to physicians with the external programmer and fine-tuned to a patient's physiological requirements prior to being programmed into the neurostimulator 12.

Therapeutically, the VNS may be delivered as a multimodal set of therapeutic doses, which are system output behaviors that are pre-specified within the neurostimulator 12 through the stored stimulation parameters and timing cycles implemented in firmware and executed by the microprocessor controller. The therapeutic doses include a maintenance dose that includes continuously-cycling, intermittent and periodic cycles of electrical stimulation during periods in which the pulse amplitude is greater than 0 mA (“therapy ON”) and during periods in which the pulse amplitude is 0 mA (“therapy OFF”).

The neurostimulator 12 can operate either with or without an integrated heart rate sensor. Additionally, where an integrated leadless heart rate monitor is available, the neurostimulator 12 can provide autonomic cardiovascular drive evaluation and self-controlled titration. Finally, the neurostimulator 12 can be used to counter natural circadian sympathetic surge upon awakening and manage the risk of cardiac arrhythmias during or attendant to sleep, particularly sleep apneic episodes.

Several classes of implantable medical devices provide therapy using electrical current as a stimulation vehicle. When such a system stimulates certain organs or body structures like the vagus nerve, therapeutic levels of electrical stimulation are usually not well tolerated by patients without undergoing a process known as titration. Titration is a systematic method or process of incrementally increasing the stimulation parameters employed by an implanted device to deliver a stimulation current to the patient at increasing levels that achieve or improve therapeutic benefit while minimizing side effects that could disrupt the stimulation therapy. Titration in a neuromodulation system may be necessary due to centrally-mediated side effects elicited by large changes in stimulation intensity. For example, the neuromodulation system may be unable to instantly change the intensity of delivered neurostimulation from an inactive state (e.g., stimulation programmed to OFF) to full therapeutic intensity without the patient experiencing adverse effects (e.g., triggering an expiratory cough reflex). That being said, the central processing areas of vagal afferents recruited at low stimulation intensity can often handle small stimulation intensity increases over periods of time without effect. As such, titration usually involves bringing the patient to an initial stimulation level that is tolerable to the patient (i.e., below an initial tolerance threshold), waiting for a period of time for the patient to adjust to the continuing delivery of the initial stimulation level and to define a higher tolerance threshold of the patient, and then increasing the initial stimulation level to a higher stimulation level that is, in some patients, greater than the initial tolerance threshold, and so on. This process is repeated in sequences that progress from a stimulation delivery provided over a waiting period, and then to an increase in a stimulation level that defines the next sequence of the stimulation delivery and the next waiting period. The central neural processors gradually remodel and accommodate the increasing stimulation intensity if given sufficient time between increasing stimulation steps (e.g., function without adverse effects such as triggering the cough reflex).

FIG. 5 is a flow diagram showing a method for delivering vagus nerve stimulation therapy, according to an exemplary embodiment. A titration process 400 is used to gradually increase the stimulation intensity to a desired therapeutic level or maintenance dosage level. If the stimulation intensity is increased too quickly before the patient is fully accommodated to the stimulation signal, the patient may experience undesirable side effects, such as coughing, hoarseness, throat irritation, or expiratory reflex. The titration process gradually increases stimulation intensity within a tolerable level and maintains that intensity for a period of time to permit the patient to adjust to each increase in intensity, thereby gradually increasing the patient's side effect tolerance zone boundary to so as to accommodate subsequent increases in intensity. The titration process continues until adequate adaptation is achieved. In embodiments, the titration process is automated and is executed by the implanted device without manual adjustment of the stimulation intensity by the subject or health care provider. As will be described in greater detail below, adequate adaptation is a composite threshold comprising one or more of the following: an acceptable side effect level, a target intensity level, and a target physiological response. In some embodiments, adequate adaption includes all three objectives: an acceptable side effect level, a target intensity level, and a target physiological response.

In some embodiments, the titration process is a mix of automation and physician input. As will be described in greater detail below, a physician may use intermediate holds to stop the automated titration at certain thresholds (e.g., a certain number of days or weeks, certain stimulation parameter values, etc.) and evaluate the patient before resuming the automated titration. The physician may receive a graphical titration history to review how the automated titration process has been progressing from one sequence to the next. The graphical titration history may include markers. The markers may represent intermediate holds, when target parameters are reached between adjacent sequences, etc. After the physician has resumed the automatic titration, the next sequence of automated titration may progress until the next intermediate hold is reached.

As described above, it may be desirable to minimize the amount of time required to complete the titration process so as to begin delivery of the stimulation at therapeutically desirable levels, particularly when the patient is being treated for an urgent condition such as CHF. In addition, it is desirable to utilize a maintenance dose intensity at the minimum level required to achieve the desired therapeutic effect. This can reduce power requirements for the neurostimulator and reduce patient discomfort.

It has been observed that a patient's side effect profile is more sensitive to the stimulation output current than to the other stimulation parameters, such as frequency, pulse width, and duty cycle. As a result, accommodation to the stimulation output current is a primary factor in completing the titration process. It has also been observed that if the other stimulation parameters are maintained at a level below the target levels, the output current can be increased to higher levels without eliciting undesirable side effects that would be result when the other parameters are at the target level. As a result, increasing the target output current while maintaining the other stimulation parameters (pulse width in particular) at reduced levels can result in a faster accommodation and shorter overall titration time than would be achieved by attempting to increase the output current while stimulating at the target pulse width.

Referring again to FIG. 5, in step 401, a stimulation system 11, including a neurostimulator 12, a nerve stimulation lead assembly 13, and a pair of electrodes 14, is implanted in the patient. In step 402, the patient undergoes an optional post-surgery recovery period, during which time the surgical incisions are allowed to heal and no VNS therapy occurs. This period may last, e.g., two weeks post-surgery. In step 403, the stimulation therapy is initiated with the initiation of a titration process. During this titration process, VNS therapy is titrated by adjusting one or more of the stimulation parameters, including output current, pulse width, signal frequency, and duty cycle, as will be described in greater detail below. Completion of the titration process determines the stimulation intensity to be used for subsequent maintenance doses delivered in step 404. These maintenance doses may be selected to provide the minimum stimulation intensity necessary to provide the desired therapeutic result.

FIG. 6A is a flow diagram illustrating a titration process 500, according to an exemplary embodiment. Process 500 includes setting titration parameters (step 501), initiating titration (step 502), stopping titration at an intermediate hold (step 503), and resuming titration (step 504).

In step 501, a physician sets the titration parameters via programmer 40, which are received by the implantable vagus nerve stimulation system 11. In some embodiments, the titration parameters may be defined by one or more titration algorithms that may be selected by the physician, or may be presented to the physician as a preferred or recommended list of titration parameters that the programming physician can adopt. In other embodiments, rather than present the physician with a set titration algorithm with fixed algorithm values, the physician may be presented with default values that could be manually adjusted. The titration parameter starting values, target values, and/or increment values for amplitude, pulse width, frequency, and/or duty cycle may be adjustable, as may the time interval between titration steps. Time of day and delay to therapy start may also be programmable as a titration parameter. The titration parameters may also include one or more intermediate holds that maintain certain parameters until the physician indicates that the automated titration can continue. The physician may be limited so that modification can be made to only a select group of parameters, or some parameters may be considered to be in a locked state until unlocked by the physician. In some embodiments, the physician is able to modify a large number of titration parameters (e.g., 10-12 parameters).

Alternatively, rather than give the physician control over the titration parameter values themselves, the physician's options for the titration process may be presented as a set of “aggressiveness” options to select from, each of which would be used by the system to determine the values to use. For example, the physician may be able to choose from an aggressive profile, a moderate profile, or a light profile (sensitive) that is appropriate for certain types of patients that do not require detailed titration parameter programming. More or fewer aggressiveness profiles could be used, and the aggressiveness profiles may correspond to the overall health status of the patient, the patient's sensitivity to stimulation therapies or titration processes, or the patient's medical history. The aggressiveness profile selected by the physician may result in a predetermined set of titration parameters being selected. The predetermined titration parameters may vary between different aggressiveness profiles, and some titration parameters may remain constant, or similar, between various aggressiveness profiles. For example, the aggressive profile may be suitable for patients that have a high toleration for the titration process and may include shorter time intervals between titration steps, higher intensity target values, and/or larger increment values (e.g., as compared to the moderate or light profiles) that may result in an achievement of a suitable therapy level more quickly as compared to the moderate or light profiles. While some of the parameters may promote a more aggressive titration progression, some of the parameters may be consistent with parameters of other profiles (e.g., titration holds).

In some embodiments, each of the aggressiveness profiles may be mapped by the system to a set of parameters or a range of parameters. For example, if the user selects the aggressive profile, the system may receive the user selection and set the values of one or more parameters (e.g., amplitude, pulse width, frequency, duty cycle, intervals between titration steps, and/or other parameters) to a first set of values. If the user selects the moderate profile, the system may set the values of the parameters to a second predetermined set or range of values that is different than the set associated with the aggressive profile. In some embodiments, the physicians are limited to modification of the parameters within a range of boundary values. The ranges may be for the default parameters, or may be set individually for the aggressiveness options (e.g., the ranges for the aggressive profile and the moderate profile may be different, but may overlap for some parameters). The physician may be able to customize the parameters in the preset profiles. Titrating according to aggressiveness profiles is described in further detail below with respect to FIGS. 13 and 14. In step 502, the physician initiates titration using the titration parameters defined at 501.

In step 503, titration is stopped at a titration hold. The titration hold may be an intermediate hold set by the physician during step 501. The VNS system 11 may perform automated titration according to process 600, described below. However, the physician is given the option (through the programmer 40) to designate intermediate points at which the titration algorithm would pause and await manual (programmer-based) activation by the physician. These hold points may be either time based (e.g. after 2, 4, 6, and/or 8 weeks of titration) or stimulation based (e.g. once stimulation amplitude reaches 1.0, 1.5, 2.0, and/or 2.5 mA). This would allow the physician to evaluate the patient in the clinic before deciding to continue titration. The physician releases the hold on the titration with the programmer 40 once the patient has been evaluated. The physician may also modify parameters during the clinical evaluations.

The holds may be predefined for the entire titration process during initial set up. Alternatively, the physician may have the option of setting a new intermediate hold when evaluating the patient. The intermediate holds may be consistent throughout the titration process (e.g., every 2 weeks, every 0.5 mA, etc.). In another embodiment, the intermediate holds are different for at least one hold (e.g., 4 weeks to the first hold, 2 weeks for every subsequent hold, etc.). In another embodiment, intermediate holds can be a combination of parameters (e.g., amplitude and pulse width). In some embodiments, the hold may be set to begin when both parameters are met or when one parameter is met. In another embodiment, one parameter cannot exceed the hold value and will remain constant until the second parameter is reached. In some embodiments, both parameters will progress according to the automated titration until both parameters meet the intermediate hold value, but one parameter may exceed the intermediate hold until the second parameter reaches the intermediate hold value. The physician may have the option to set as many or as few intermediate holds as desired.

During the automated titration between intermediate holds, the VNS system 11 may be fully automated or partially automated. In some embodiments, titration is performed without any intervention from either the patient or the healthcare provider. This embodiment also automatically detects patient side effects and intolerance and adjusts stimulation parameters to remain below the side effect threshold, as is described with respect to FIG. 6B. In another embodiment, the VNS system 11 may automatically adjust stimulation parameters slowly over time, without any additional intervention from the healthcare provider. Because the system may not be able to determine if stimulation causes an intolerable side effect, it may be configured to rely on the patient to swipe a magnet to indicate an intolerable level of a side effect. The VNS system 11 may then adjust stimulation parameters in response to patient magnet activation.

For example, patients may require a total of 10±2 clinic visits over a 10-week period to reach the target stimulation intensity. The frequency of required clinic visits is bothersome to both patients and providers and creates a barrier to therapy adoption. In addition, the frequency of required clinic visits extends the time required to titrate patients to the target stimulation intensity. However, the physician may be skeptical of completely automated titration and want to ensure the patients are not experiencing intolerable side effects and are adapting to stimulation adequately. By allowing the physician to set the parameters, and evaluate the patient intermediately, but still allow titration to perform automatically between visits, the time period to reach the target stimulation may be reduced, while giving the physicians more control over the titration process. Preferably, the number of clinic visits needed and the overall timeframe of the titration process is reduced by only the use of intermediate holds. Any time penalty related to the intermediate holds is believed to be significantly less than the time penalty resulting from an automated titration process that causes side effect and ultimately requires the patient to undergo a re-titration protocol.

In step 504, titration is resumed. The physician may resume titration using the programmer 40 after evaluation of the patient. When the physician resumes titration, he or she may have the option to modify stimulation parameters and/or intermediate holds. The titration may resume using automated titration until the next intermediate hold is reached. This process may continue until the therapy parameters are reached.

FIG. 6B is a flow diagram illustrating a titration process 600 in accordance with exemplary embodiments. When first initiating the titration process, the neurostimulator 12 is configured to generate a stimulation signal having an initial stimulation parameter set. The initial parameter set may comprise an initial output current, an initial frequency, an initial pulse width, and an initial duty cycle. The various initial parameter settings may vary but may be selected so that one or more of the parameters are set at levels below a predefined target parameter set level, such that the titration process is used to gradually increase the intensity parameters to achieve adequate adaptation. In some embodiments, the initial frequency is set at the target frequency level, while the initial output current, initial pulse width, and initial duty cycle are set below their respective target levels. In one embodiment, the target parameter set comprises a 5 Hz frequency, 250 μsec pulse width, a duty cycle of 14 sec ON and 66 seconds OFF, and an output current of between 1.5 mA-3.0 mA (e.g., 2.5 mA for right side stimulation and 3.0 mA for left side stimulation), and the initial parameter set comprises 5 Hz frequency, 130 μsec pulse width, a duty cycle of 14 sec ON and 66 seconds OFF, and an output current of between 0.25 mA-0.5 mA. In other embodiments, the target parameter set includes a 10 Hz frequency that is used instead of a 5 Hz frequency. The initial parameter set may also include one or more intermediate holds as discussed with respect to FIG. 6A. However, this is an exemplary embodiment and these values are not intended to be limiting. Other frequencies, pulse widths, duty cycles and output currents may be implemented. The initial and target parameters may vary from patient to patient based on the patient's sensitivity to stimulation. While the initial parameters are shown to be equal to the target parameters for some of the exemplary parameters (e.g., frequency and duty cycle), some or all of the parameters may have initial parameters that differ from the target parameters.

In step 601, the stimulation system delivers stimulation to the patient. If this is the first titration session, then the stimulation would be delivered with the initial stimulation parameter set described above. If this is a subsequent titration session, then the stimulation intensity would remain at the same level provided at the conclusion of the previous titration session. Alternatively, the subsequent titration session can start at a level that is set by the physician, e.g., at the next titration level that follows the level provided at the conclusion of the previous titration session.

In step 602, the output current is gradually increased until the stimulation results in an intolerable side effect level, the target intensity (e.g., 2.5 mA at a pulse width of 250 μs and a frequency of 10 Hz) is reached, or adequate adaptation is achieved. As described above, adequate adaptation is a composite threshold comprising one or more of the following: an acceptable side effect level, a target intensity level, and a target physiological response. In accordance with some embodiments, the target physiological response comprises a target heart rate change during stimulation. The patient's heart rate may be monitored using an implanted or external heart rate monitor, and the patient's heart rate during stimulation is compared to the patient's baseline heart rate to determine the extent of heart rate change. In accordance with some embodiments, the target heart rate change is a heart rate change of between 4% and 5%. If at any point during the titration process 600 adequate adaptation is achieved, the titration process ends, and the stimulation intensity which resulted in the adequate adaptation is used for ongoing maintenance dose therapy delivery.

The output current may be increased in any desired increment, but small increments, e.g., 0.1 mA or 0.25 mA, may be desirable so as to enable more precise adjustments. In some cases, the output current increments may be determined by the neurostimulator's maximum control capability. During the initial titration sessions, it is likely that the patient's side effect tolerance zone boundary will be reached well before the output current reaches the target level or adequate adaptation is achieved. At decision step 603, if the target output current has not been achieved but the maximum tolerable side effects have been exceeded, the process proceeds to step 604.

In step 604, the output current is reduced one increment to bring the side effects within acceptable levels. In addition, the frequency is reduced. In embodiments in which the initial frequency was 10 Hz, in step 604, the frequency may be reduced, e.g., to 5 Hz or 2 Hz.

Next, in step 605, the output current is gradually increased again at the reduced frequency level until the stimulation results in an intolerable side effect level or the target output current (e.g., 2.5 mA) is reached. At decision step 606, if the target output current has been reached and the maximum tolerable side effects have not been exceeded, the process proceeds to step 607 where the titration session is concluded. The stimulation system may be programmed to continue delivering the stimulation signal at the last parameter settings achieved prior to conclusion of the titration session. After a period of time, another titration session may be initiated and the process returns to step 601. This can be any period of time sufficient to permit the patient to adjust to the increased stimulation levels. This can be, for example, as little as approximately two or three days, approximately one to two weeks, approximately four to eight weeks, or any other desired period of time.

In some embodiments, the titration sessions are automatically initiated by the stimulation system or initiated by the patient without requiring any intervention by the health care provider. This can eliminate the need for the patient to schedule a subsequent visit to the health care provider, thereby potentially reducing the total amount of time needed for the titration process to complete. In these embodiments, the stimulation system may include a physiological monitor, e.g., an implanted heart rate sensor, that communicates with the stimulation system's control system to enable the control system to detect the patient's physiological response to the titration and automatically make adjustments to the titration processes described herein with reduced or no inputs from the patient or health care provider. The monitored signals can also enable the control system to detect when the target physiological response has been achieved and conclude the titration process. The stimulation system could in addition or alternatively include a patient control input to permit the patient to communicate to the control system that the acceptable side effect level has been exceeded. This control input may comprise an external control magnet that the patient can swipe over the implanted neurostimulator or other internal or external communication device that the patient can use to provide an input to the control system. In these automatically-initiated titration sessions, the stimulation system may be configured to wait a period of time after completing one session before initiating the next session. This period of time may be predetermined, e.g., two or three days, or programmable. In another embodiment, the stimulation system is configured to wait until authorization has been received before initiating the next session (i.e., an intermediate hold).

Returning to decision step 606, if the target output current has not been reached but the maximum tolerable side effects have been exceeded, the process proceeds to step 608. In step 608, the output current is reduced one increment to restore an acceptable side effect condition, and the frequency is gradually increased until the stimulation results in an intolerable side effect level or the target frequency (e.g., 5 Hz) is reached. At decision step 609, if the target frequency has not been reached but the maximum tolerable side effects have been exceeded, the frequency is reduced to restore an acceptable side effect level and the process proceeds to step 607. Again, in step 607, the current titration session is concluded, and the stimulation system may be programmed to continue delivering the stimulation signal at the last parameter settings achieved prior to conclusion of the titration session.

At decision step 609, if the target frequency has been reached before the maximum tolerable side effects have been exceeded, the duty cycle is gradually increased until the stimulation results in an intolerable side effect level or the target duty cycle (e.g., 14 sec ON and 66 sec OFF) is reached, at which point the process proceeds to step 607 and the titration session is concluded and ongoing stimulation delivered at the last intensity eliciting acceptable side effect levels.

Returning to decision step 603, if the target output current has been achieved before the maximum tolerable side effects are exceeded, the process proceeds to step 611. In step 611, the pulse width is gradually increased until the stimulation results in an intolerable side effect level or the target pulse width (e.g., 250 μsec) is reached. In some embodiments, before step 611, the output current is reduced (e.g., by up to 50%), and the pulse width may be increased in step 611 at that reduced output current. After the target pulse width is achieved, the output current may be restored to the target output current. In other embodiments, the output current may be reduced (or may be retained at the reduced level established prior to step 611, as described above), and the frequency and duty cycle are gradually increased in step 613 at that reduced output current. This reduction in output current after achieving the target output current may enable the patient to maintain tolerability with increasing pulse width, frequency, and duty cycle in subsequent titration steps.

At decision step 612, if the target pulse width has not been achieved before the maximum tolerable side effects have been exceeded, the pulse width is reduced to restore an acceptable side effect level and the process proceeds to step 607. Again, in step 607, the current titration session is concluded.

If at decision step 612, the target pulse width has been achieved before the maximum tolerable side effects have been exceeded, the process proceeds to step 613. In step 613, the frequency and/or duty cycle are increased until the stimulation results in an intolerable side effect level or the target frequency and target duty cycle are reached. The frequency and duty cycle can be increased in step 612 simultaneously, sequentially, or on an alternating basis.

At decision step 614, if the target frequency and/or target duty cycle have not been achieved before the maximum tolerable side effects have been exceeded, the pulse width and/or frequency are reduced to restore an acceptable side effect level, and the process continues to step 607 and the titration session is concluded. In some embodiments, the conclusion of the titration session represented in step 607 indicates an intermediate hold has been reached. A new titration session could then be initiated after visiting a physician to release the intermediate hold.

At decision step 614, if the target pulse width and target frequency have been achieved before the maximum tolerable side effects have been exceeded, all of the stimulation parameters will have reached their target levels and the titration process concludes at step 615. The stimulation therapy may proceed with the maintenance dose at the target stimulation levels. In some embodiments, the target frequency and duty cycle achieved are for a given titration session with an intermediate hold. In this case, the patient would visit a health care provider or physician for an evaluation. The physician would then release the hold on the titration processes or initiate the beginning of therapy.

In some embodiments, in step 604, instead of reducing the frequency in order to facilitate increase of the output current, the pulse width may be reduced. For example, embodiments where the target pulse width is 250 μsec, the pulse width may be reduced, e.g., to 150 μsec or less. Then, the method proceeds to step 605, in which the output current is gradually increased again at the reduced pulse width level until the stimulation results in an intolerable side effect level or the target output current (e.g., 2.5 mA) is reached.

Therapy can also be autonomously titrated by the neurostimulator 12 in which titration progressively occurs in a self-paced, self-monitored fashion. The progression of titration sessions may occur on an autonomous schedule or may be initiated upon receipt of an input from the patient. Ordinarily, the patient 10 is expected to visit his healthcare provider to have the stimulation parameters stored by the neurostimulator 12 in the recordable memory 29 reprogrammed using an external programmer. Alternatively, the neurostimulator 12 can be programmed to automatically titrate therapy by up titrating the VNS through periodic incremental increases using titration sessions as described above. The titration process 600 will continue until the ultimate therapeutic goal is reached.

Following the titration period, therapeutic VNS, as parametrically defined by the maintenance dose operating mode, is delivered to at least one of the vagus nerves. The stimulation system 11 delivers electrical therapeutic stimulation to the cervical vagus nerve of a patient 10 in a manner that results in creation and propagation (in both afferent and efferent directions) of action potentials within neuronal fibers of either the left or right vagus nerve independent of cardiac cycle.

FIG. 7A is a simplified block diagram of an implanted neurostimulation system 700, according to an exemplary embodiment. The implanted neurostimulation system 700 comprises a control system 702 comprising a processor programmed to operate the system 700, a memory 703, an optional physiological sensor 704, and a stimulation subsystem 706. The physiological sensor 704 may be configured to monitor any of a variety of patient physiological signals, and the stimulation subsystem 706 may be configured to deliver a stimulation signal to the patient. In one example, the physiological sensor 704 comprises an ECG sensor or an accelerometer for monitoring heart rate, and the stimulation subsystem 706 comprises a neurostimulator 12 programmed to deliver ON-OFF cycles of stimulation to the patient's vagus nerve. The implanted system 700 may include a patient input sensor 705, described in more detail below.

The control system 702 is programmed to activate the neurostimulator 12 to deliver stimulation signals at varying stimulation intensities to the patient and to monitor the physiological signals in response to those delivered stimulation signals.

The external programmer 707 shown in FIG. 7A may be utilized by a clinician or by the patient for communicating with the implanted system 700 to adjust parameters, activate therapy, retrieve data collected by the system 700, or provide other input to the system 700. In some embodiments, the external programmer 707 may be used remotely from the implanted system 700 (e.g., when the patient is not at a clinic). For example, instead of the patient coming into the clinic for a check-up during a titration hold, the clinician may check on the patient remotely (e.g., phone call, video call, etc.). The clinician could then use the external programmer 707 to activate the next titration session or modify parameters of the titration. In some embodiments, the external programmer 707 may provide an alert indicating the patient has reached a titration hold. In some embodiments, the patient receives an alert indicating a titration hold has been reached (e.g., email, text message, etc.). In some such embodiments, the external programmer 707 may include communication circuitry adapted to communicate over a long distance using one or more protocols (e.g., cellular, Internet, etc.). In some embodiments, the external programmer 707 may be configured to program the implanted system 700 with a prescribed time or window of time during which titration sessions may be initiated, as described in further detail below with respect to FIGS. 16 and 17. This can be used, for example, to prevent a titration session from occurring at night when the patient's sleep is likely to be disturbed by the increase in stimulation intensity and resulting side effects.

Patient inputs to the implanted system 700 may be provided in a variety of ways. The implanted system 700 may include a patient input sensor 705. As described above, a patient magnet 730 may be used to provide external input to the system 700. When the patient magnet 730 is placed on the patient's chest in close proximity to the implanted system 700, the patient input sensor 705 will detect the presence of the magnetic field generated by the patient magnet 730 and provide a control input to the control system 702. The system 700 may be programmed to receive patient inputs to set the time of day during which titration sessions are to be initiated.

In other embodiments, the patient input sensor 705 may comprise a motion sensor, such as an accelerometer, which is configured to detect tapping on the surface of the patient's chest. The patient may use finger taps in one or more predetermined patterns to provide control inputs to the implanted system 700. For example, when the motion sensor detects three rapid taps to the patient's chest, that may trigger an operation on the implanted system 700 (e.g., to initiate a titration session). Alternatively, if the motion sensor detects a predetermined pattern of taps during a titration session, the implanted system 700 will interpret those taps as a patient input indicating that the patient's tolerance zone boundary has been exceeded.

In other embodiments, the patient input sensor 705 may comprise an acoustic transducer or other sensor configured to detect acoustic signals. The system 700 may be programmed to interpret the detection of certain sounds as patient inputs. For example, the patient may utilize an electronic device, such as a smartphone or other portable audio device, to generate one or more predetermined sequences of tones. The system 700 may be programmed to interpret each of these sequences of tones as a different patient input.

The titration of the stimulation signal delivery and the monitoring of the patient's physiological response (e.g., heart rate) may be advantageously implemented using a control system 702 in communication with both the stimulation subsystem 706 and the physiological sensor 704, such as by incorporating all of these components into a single implantable device 700. In accordance with other embodiments, an external control system 712 may be implemented in a separate implanted device or in an external programmer 720 or other external device, as shown in FIG. 7B to provide control over and communication with an implanted physiological sensor 714 and a stimulation subsystem 716 similar to those describe with regard to FIG. 6A. The external programmer 720 in FIG. 7B may be utilized by a clinician or by the patient for adjusting stimulation parameters. The external programmer 720 may be in wireless communication with the implanted medical device 710, which includes the stimulation subsystem 716 and a memory 713. In the illustrated embodiment, the physiological sensor 714 is incorporated into the implanted medical device 710, but in other embodiments, the sensor 714 may be incorporated into a separate implanted device, may be provided externally and in communication with the external programmer 720, or may be provided as part of the external programmer 720.

When monitoring the patients, the physician uses the external programmer 707 to connect with the implantable medical device 710. However, in some implementations, the physician must manually connect the external programmer 707 to each implantable medical device 710 to perform titration functions (e.g., change parameter settings, titration holds and settings, etc.), which can be burdensome on physicians, as well as the clinic. FIGS. 8-10 address this issue, according to example embodiments, by providing a dashboard capable of monitoring a plurality of patients, even when the patients are not in the clinic.

FIG. 8 is a titration assist management dashboard 800, according to an exemplary embodiment. The titration assist management dashboard 800 operates on a device 802 with a display 804. The display 804 provides the dashboard 800 which includes information relating to patient name 806, patient status 808, patient priority 810 and patient notes 812.

The device 802 includes a processor, memory, a communication circuit, and various input and output circuits. The device 802 may be a programming computer (e.g., programming computer 41, external programmer 707) that is in direct communication with a programming wand (e.g., programming wand 42). In some embodiments, the device 802 may be a computer, a tablet, a handheld device, a wearable, etc. In some embodiments, the device 802 is capable of communicating directly with an implantable medical device (e.g., telemetry). In some embodiments, the device 802 that is capable of communicating with a secondary device (e.g., a programming computer) that communicates with an implantable medical device. In some embodiments, the device 802 can communicate with a remote device that is not located at the physician's office, such as a home monitor. The device 802 may communicate with the secondary device via telemetry, a wired connection, or another device/method of communication. In some embodiments, the device 802 is in communication with a website, server, program, etc. that allows the device 802 to access the dashboard 800. For example, the dashboard 800 may be accessible on multiple devices 802 at the same time.

The dashboard 800 includes information relating to patient name 806, patient status 808, patient priority 810, and/or patient notes 812. The dashboard 800 compiles patient information when a patient is set up on a titration assist program. Once the patient information is in the dashboard 800, the dashboard 800 is able to monitor patient status without being in communication with the implantable medical device by knowing the parameters of the titration assist and updating the dashboard according to the titration assist parameters, in some implementations.

For each patient, the dashboard 800 provides patient name 806, patient status 808, patient priority 810, and/or patient notes 812. In order to use the dashboard 800, a user (e.g., physician, nurse, medical assistant, etc.) may provide log in credentials. In some embodiments, the amount or detail of information provided may vary based on the log in information provided. For example, the physician may have access to all the information provided on the dashboard 800, while the information provided to a nurse or medical assistant may be more limited.

The patient name 806 provided on the dashboard 800 may be the actual name of the patient, or a means of identifying the patient while maintaining anonymity of the patient (e.g., patient identification number, etc.). In some embodiments, the patient name 806 may also provide information relating to general patient information (e.g., home address, contact information, medical history, age, gender, insurance information, etc.). While all this information may not be present on a main screen of the dashboard 800 (e.g., as shown in FIG. 8), the user may be able to access the additional information by selecting a specific patient.

The patient status 808 provided on the dashboard 800 is a status of the progression of the titration based on the titration assist parameters established during interrogation of the implantable medical device. The patient status 808 may include a stimulation parameters (e.g., amplitude, frequency, pulse width, etc.). In some embodiments, the patient status 808 may also indicate if a HOLD is present in the titration progression, an indication of the weeks that have passes since titration has started, or another indication of the time of titration. The dashboard 800 is able to update the patient status 808 based on the settings of titration, such as updating the patient status 808 to indicate a hold is present.

The dashboard 800 may also include patient notes 812. The patient notes 812 may include a plurality of information relating to the patient, titration, and other information the physician feels may be pertinent. For example, the patient notes 812 may include the aggression profile that was selected for the patient, initial titration parameters, target stimulation parameters, settings for stimulation increases, titration hold settings, a parameter setting profile, patient side effects, etc. The patient notes 812 may be a text box or a plurality of text boxes where the user can insert a variety of notes. In some embodiments, the patient notes 812 are a plurality of check boxes or other selection mechanisms that provides a list of parameters, settings, side effects, etc. that can be selected. In some embodiments, the patient notes 812 are a combination of check boxes and text boxes to provide diverse means of recording patient notes 812. The patient notes 812 may all be present on the dashboard 800. In some embodiments, only a portion of the patients notes 812 are provided on a main screen of the dashboard 800. In some embodiments, the user may be able to select which patient notes 812 are present on the main screen of the dashboard 800. In some embodiments, a default set of patient notes 812 are present on the main screen of the dashboard 800. In some embodiments, the dashboard 800 can create patient notes based on the patient status 808. For example, if the patient status 808 is updated to indicate a hold has been reached, the patient notes 812 may be updated to indicate a follow up appointment or call needs to be scheduled.

The patient priority 810 indicates a likelihood of the patient needing attention (e.g., most likely to need a clinical visit). The patient priority 810 may be based on a combination of patient status 808, patient information contained within the patient name 806, and patient notes 812. The patient status 808, patient information contained within the patient name 806, and patient notes 812 may receive a value based on the information contained within. The patient priority 810 may be a weighted combination of the values of the patient status 808, patient information contained within the patient name 806, and patient notes 812. In some embodiments, the information contained in the patient notes 812 may be individually valued and/or weighted based on the information contained (e.g., aggression profile, target stimulation, side effects, etc.). Some side effects may be indicated as more severe than others, and the dashboard 800 may assign a different value or weight relating to different side effects. In addition, patients may be more prone to side effects during different stages of titration based on the intensity of titration, which again could receive different values or weighting by the dashboard 800. Patients may also be more or likely to develop various side effects, or experience the side effects more severely based on tolerance; this can be taken into account by the dashboard 800 when determining patient priority 810.

The patient priority 810 may be selected depending on a value of the weight profile crossing one or more thresholds defining various patient priorities 810. In some embodiments, the patient priority 810 may be independent of a priority calculated for another patient (i.e., multiple patients may have the same priority level). In some embodiments, the patient may be compared to some or all of the other patients in the dashboard 800 to provide a unique patient priority 810 to each patient. In some embodiments, custom patient priorities 810 may be established by the physician based on physician knowledge that may not be recognized by the dashboard 800.

The dashboard 800 may also provide addition functions for the physician to interact with and analyze patient information. In some embodiments, the dashboard 800 can provide a log of interactions with the dashboard 800. In some embodiments, the dashboard 800 provides a log of interactions based on the patient, the person who was logged in, insurance, etc.

In some embodiments, the dashboard 800 provides controls for the physician to collect and analyze physiological data of the patient, modify stimulation parameters, and monitor and modify stimulation holds. In some embodiments, the dashboard 800 collects physiological patient data through remote communication with the implantable medical device of the patient or a home monitoring system of the patient. In some embodiments, the physiological data can be updated for a patient in real time. In some embodiments, the physiological data is provided to the dashboard 800 periodically (e.g., daily, weekly, etc.).

In some embodiments, the dashboard 800 provides functions allowing a user to modify stimulation parameters. The stimulation parameters can be modified by changing an aggression profile, target parameter settings, titration step settings, etc. In some embodiments, the stimulation parameters can be remotely modified at any time. The patient may be notified to provide an update via a home monitoring unit. In some embodiments, the stimulation parameters are limited to remote modifications during specific times of the titration process (e.g., titration holds). In some embodiments, the remote modification of the stimulation parameters is limited. For example, the parameters can only be modified by certain predefined amounts, maximum amounts, or other limitations. In some embodiments, the modified stimulation parameters are updated in the implantable medical device with a home monitoring device. In some embodiments, the patient is alerted of an update and must take action to update the implantable medical device. In some embodiments, the implantable medical device is automatically updated.

In some embodiments, the physician is able to modify the hold settings of the titration for any given patient. In some embodiments, the physician can initiate a hold, clear a hold, modify the parameter level at which a hold is initiated, add additional holds, or modify the holds in other ways. Therefore, if the physician notices physiological data of the patient is indicating adverse side effects, if the dashboard 800 alerts the physician of adverse side effects, if the patient contacts the physician regarding adverse side effects, etc., then the physician can initiate a hold for the titration settings of the patient using the dashboard 800. In some embodiments, the physician can initiate a hold with parameters different than the parameters that caused adverse side effects. By initiating the hold, the physician can schedule time to talk to the patient on the phone or in the office without allowing the adverse side effects to continue or worsen.

In some embodiments, the physician can clear a hold remotely using the dashboard 800. For example, a physician may talk to the patient over the phone to determine if the patient is experiencing any adverse side effects once the dashboard 800 indicates a hold for the patient. The physician can then remotely clear the hold if no adverse side effects are being experienced by the patient.

In some cases, after the initial parameter and titration settings have been established, the physician may determine that a patient is more or less prone to side effects than initially determined. Accordingly, in some embodiments, the physician is able to modify the parameter settings associated with a future hold (e.g., instead of having a hold at 1.5 mA, have a hold at 2.0 mA), without modifying the titration settings, such that the hold occurs sooner or later that initially established. In some embodiments, the physician can add or remove a future hold instead of, or in addition to, modifying the parameter settings associated with a hold.

In some embodiments, the holds are updated in the implantable medical device with a home monitoring device of the patient. In some embodiments, the patient is alerted of an update and must take action to update the implantable medical device. In some embodiments, the implantable medical device is automatically updated.

FIG. 9 is a patient titration graph 900 of the titration assist management dashboard 800 of FIG. 8, according to an exemplary embodiment. The user can select a patient on the dashboard 800 to view in further detail. By selecting a patient, the user can see the titration graph 900 that is specific to the selected patient. The graph 900 includes an x-axis 902, a y-axis 904, a stimulation level 906, one or more holds 908, and a current stimulation setting 910.

The x-axis 902 is a unit of time (e.g., days, weeks, months, etc.), while the y-axis 904 is a parameter of stimulation (e.g., amplitude, frequency, duty cycle, etc.). In some embodiments, the user can change the units of the x-axis 902 and the y-axis 904 to provide alternative views of the titration settings. The stimulation level 906 is shown based on the units set for the x-axis 902 and the y-axis 904. While the stimulation level 906 is shown in FIG. 9 as increasing uniformly, the stimulation level 906 is based on the titration parameters set forth, which may not increase in a uniform fashion.

The stimulation level 906 also includes the titration holds 908 that were established during set up of titration. The titration holds 908 may be set at equal intervals or may be set at varying intervals, based on the requirements set forth during set up. In some embodiments, the titration graph 900 also includes a marker showing the current stimulation setting 910. The current stimulation setting 910 indicates the progression of the titration so the user can easily see how soon the next hold 908 will occur and the current stimulation setting 910, past and future stimulation levels 906.

FIG. 10 is a flowchart of a process 1000 for managing patients using the titration assist management dashboard 800, according to an exemplary embodiment. The process 1000 includes receiving a plurality of patient information at 1002, evaluating each patient at 1004, determining a status of each patient at 1006, determining a priority of each patient at 1008, and sorting the patients based on user input at 1010.

The titration assist management dashboard 800 receives the plurality of patient information at 1002. In some embodiments, the titration assist management dashboard 800 receives patient information relating to a single patient one at a time. In some embodiments, the titration assist management dashboard 800 receives patient information relating to multiple patients at once. In some embodiments, the titration assist management dashboard 800 receives patient information by wirelessly communicating with an individual implantable medical device for each patient. In some embodiments, the titration assist management dashboard 800 receives patient information via wired or wireless communication with a programming wand. In some embodiments, the titration assist management dashboard 800 receives patient information via wireless communication with a remote device (e.g., home monitor, etc.). In some embodiments, the titration assist management dashboard 800 receives patient information via communication with another device located in the physician's office or the patient's home. In some embodiments, a user of the titration assist management dashboard 800 must actively prompt the titration assist management dashboard 800 to receive patient information. In some embodiments, the titration assist management dashboard 800 automatically collects patient information when certain criteria are met (e.g., device with patient information connected, device with patient information identified, patient is not currently in titration assist management dashboard, etc.). The patient information may include patient name, address, number, insurance information, titration assist parameters, patient notes 812, etc.

The titration assist management dashboard 800 evaluates each patient based on the patient information at 1004. The titration assist management dashboard 800 may evaluate the patient information to determine if any required information is missing (e.g., name, insurance information, titration settings, etc.). In some embodiments, the titration assist management dashboard 800 prompts a user to enter the missing information (e.g., a pop-up screen, alert, etc.). In some embodiments, the titration assist management dashboard 800 flags a patient as having missing information (e.g., change in color, marking by patient, etc.). In some embodiments, the titration assist management dashboard 800 evaluates the patient information to determine if the patient is likely to obtain side effects from titration or need additional contact with the physician. In some embodiments, the titration assist management dashboard 800 evaluates patient height, weight, gender, titration settings, notes etc. to determine if the patient is likely to obtain side effects from titration or need additional contact with the physician.

The titration assist management dashboard 800 determines a status of each patient at 1006. As described above, the patient status is the status of the progression of the titration based on the titration assist parameters established during interrogation of the implantable medical device. The patient status may include a stimulation parameters (e.g., amplitude, frequency, pulse width, etc.). In some embodiments, the patient status may also indicate if a HOLD is present in the titration progression, an indication of the weeks that have passes since titration has started, or another indication of the time of titration. The titration assist management dashboard 800 is able to update the patient status based on the settings of titration, such as updating the patient status to indicate a hold is present. The patient status may be updated periodically (e.g., daily, weekly, when a titration setting changes, etc.) without being in communication with the implantable medical device by knowing the parameters of the titration assist and updating the dashboard according to the titration assist parameters that are recorded in the titration assist management dashboard 800.

The titration assist management dashboard 800 determines a priority of each patient at 1008, in some implementations. The patient priority indicates a likelihood of the patient needing attention (e.g., most likely to need a clinical visit). The patient priority may be based on a combination of patient status, patient information contained within the patient name, and patient notes. The patient status, patient information contained within the patient name, and patient notes may receive a value based on the information contained within. The patient priority may be a weighted combination of the values of the patient status, patient information contained within the patient name, and patient notes. In some embodiments, the information contained in the patient notes 812 may be individually valued and/or weighted based on the information contained (e.g., aggression profile, target stimulation, side effects, etc.). Some side effects may be indicated as more severe than others, and the dashboard 800 may assign a different value or weight relating to different side effects. In addition, patients may be more prone to side effects during different stages of titration based on the intensity of titration, which again could receive different values or weighting by the dashboard. Patients may also be more or less likely to develop various side effects, or experience the side effects more severely, based on tolerance; this can be taken into account by the titration assist management dashboard 800 when determining patient priority.

The patient priority may be selected depending on a value of the weight profile crossing one or more thresholds defining various patient priorities. In some embodiments, the patient priority may be independent of a priority calculated for another patient (i.e., multiple patients may have the same priority level). In some embodiments, the patient may be compared to some or all of the other patients in the titration assist management dashboard 800 to provide a unique patient priority to each patient. In some embodiments, custom patient priorities may be established by the physician based on physician knowledge that may not be recognized by the titration assist management dashboard 800.

The titration assist management dashboard 800 may indicate patient priority in a variety of ways. In some embodiments, the patients are color coded based on patient priority (e.g., red for high priority, green for low priority, etc.). In some embodiments, the patient priority is a number. In some embodiments, the patient priority is a symbol, marker, or other visual indication of patient priority.

The titration assist management dashboard 800 sorts the patients based on user input at 1010. The user may be able to select a default setting for sorting the patients, such that if no sorting has been selected, the patients will be sorted according to the default setting. The user may be able to sort the patients based on patient name, patient information, patient status, patient priority, etc. In some embodiments, the patients can be sorted in ascending or descending order based on the selected criteria.

By creating a dashboard (e.g., dashboard 800), a physician can monitor a plurality of patients with a single device. The physician is able to easily view the status of any patient without having to interrogate their implantable medical device. In addition, if a patient calls the physician's office, the physician can determine what the stimulation parameters are for titration and may be able to evaluate the patient over the phone or recommend that the patient come into the office for a check-up based on urgency and severity. The physician can also take notes on the dashboard based on information received from the patient during the call.

As discussed above, the VNS system 11 may perform fully automated or partially automated titration of VNS stimulation parameters. For example, in some arrangements, the VNS system 11 performs automated titration of VNS stimulation parameters between an initial stimulation intensity and a hold intensity prescribed by the patient's physician (e.g., by making small, periodic stimulation intensity increases between the initial and hold intensities). Once the hold intensity is reached, the patient must visit the physician. The physician evaluates the patient for side effects and decides whether to remove the hold and continue titration. This process is continued until the stimulation reaches a physician-prescribed target intensity. In other arrangements, the physician sets an initial stimulation intensity and a target stimulation intensity. The VNS system 11 then performs titration by automatically making small, periodic stimulation intensity increases between the initial and target intensities such that the patient's nervous system is allowed to accommodate to each new intensity. Once the target intensity is achieved, the patient returns to the physician for final intensity adjustments. As such, evaluation of the heart rate effects at higher stimulation intensities occur while the patient is in the clinic environment with appropriate physiological monitoring.

One advantage of performing titration in this manner is that this method of titration reduces or eliminates patient and physician workloads as the patient does not need to visit the clinic for any titration adjustment. The frequency of titration can also occur at a rate of adjustment (e.g., multiple small titration step increases per day) that would otherwise not be practically feasible for patients using existing alternatives of on-site visits for every programmed adjustment. Moreover, this method of titration assures that the patient receives therapeutic levels of stimulation quickly while simultaneously minimizing the likelihood of serious adverse effects (e.g., minimizing the chances of the patient developing symptomatic bradycardia). To illustrate, a traditional titration method may require 8-12 clinic visits, 12-18 hours of programming time, and 24-48 hours of patient time exposure. Yet, the traditional titration method may only allow for 6-10 therapy adjustments with 10-12 weeks required until the stimulation intensity reaches therapeutic levels. By contrast, the present systems and methods for titration may require only 2 clinic visits, 2 hours of programming time, and 6 hours of patient time exposure, while allowing for 25+ therapy adjustments with only 4-6 weeks required until the stimulation intensity reaches therapeutic levels.

Moreover, in various embodiments, the VNS system 11 may be programmable with high resolution stimulation parameters that enable physicians to use an optimal set of stimulation parameters (e.g., current amplitude, frequency, pulse width, ON-time and OFF-time). As an illustration, physicians may be able to fine-tune therapy around the patient's neural fulcrum (i.e., an operating point formed by a combination of stimulation intensity and duty cycle that gives rise to a small and repeatable reduction in heart rate) using the high resolution parameters. These high resolution stimulation parameters improve the titration experience for the patient by enabling smaller intensity steps, which allows patients to reach a therapeutic range without requiring a clinic visit for every stimulation adjustment.

Additionally, automatic adjustment of the stimulation parameters may occur according to settings programmed by the physician or modified or selected by the physician from factory settings. For example, the physician may be able to select from specific parameters provided by the VNS system 11 or from a parameter range provided by the VNS system 11. As an illustration, the physician may be able to select between 0.125 mA (for 0.0 to 1.875 mA initial to target intensities) and 0.25 mA (for 2.0 to 3.5 mA target intensities) current amplitude increments; 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, and 20 Hz frequency increments; and 130, 150, 180, 210, 250, 275, 300, 370, and 500 μs pulse width increments, with the stimulation occurring according to a default duty cycle (e.g., 14 seconds ON and 66 seconds OFF, with a 2 second ramp-up and a 2 second ramp-down). Alternatively, the automatic adjustment may occur based entirely or almost entirely on factory setting, such as on a factory-adjustable fixed time interval (e.g., four steps per day), during fixed time periods (e.g., only during the daytime when the patient is less likely to be asleep, as described below with reference to FIGS. 16 and 17), according to fixed trajectories (e.g., as shown in FIG. 13), and so on. The VNS system 11 may then determine whether any changes should be made to the stimulation parameters and, if so, which changes should be made during the titration process.

As an example, a physician may set (e.g., via the external programmer 40) the initial stimulation intensity (e.g., zero stimulation, with a 0 mA amplitude, 60 μs pulse width, and 5 Hz frequency) and the target stimulation (e.g., 1.5-2.0 mA amplitude, 250 μs pulse width, and 5 Hz frequency). The VNS system 11 may then dictate titration according to an algorithm such that four titration steps (e.g., 0.125 mA, 30 μsec, and/or 0.1 Hz steps, which result in smooth intensity increases over time) are implemented a day with no changes permitted between 1:00 and 6:00 AM (e.g., to avoid the possibility that the patient may go to sleep with no side effects but later wake up from the side effects, such as a cough). Once the target stimulation is reached, the physician may make further adjustments as the patient will likely tolerate the adjustments due to the patient's nervous system having become accommodated to the stimulation.

In various embodiments, the VNS system 11 may be programmed (e.g., by the external programmer 40 or the recordable memory 29 can contain certain instructions when the neurostimulator 12 is implanted) to perform the titration according to a stimulation profile adapted to reduce patient side effects during the titration process. As an illustration, FIG. 11 is a patient titration graph 1100 incorporating a “dwell point,” according to an exemplary embodiment. The graph 1100 includes an x-axis 1102 and a y-axis 1104. The x-axis 1102 is a unit of time (e.g., days, weeks, months, etc.), while the y-axis 1104 is a parameter of stimulation (e.g., amplitude, frequency, duty cycle, etc.). In various embodiments, the titration graph 1100 may be incorporated in a user interface displayed to a physician (e.g., on the external programmer 40 or other computing device) during the titration configuration process.

The graph 1100 includes three titration rates at which at least one stimulation parameter (e.g., output current, frequency, pulse width, duty cycle, etc.) is increased. In various embodiments, each of the three titration rates are configured such that the at least one stimulation parameter is gradually increased. The titration according to FIG. 11 initially occurs at a first rate 1106 until the at least one stimulation parameter reaches a first target value 1108. Subsequently, the titration shifts to a second rate 1110, which is less than the first rate 1106. Because the at least one parameter is increased more slowly during this portion of the titration, the second rate 1110 marks a “dwell point” in the graph 1100. The titration occurs according to the second rate 1110 until the at least one stimulation parameter reaches a second target value 1112. Once the second target value 1112 is reached, the titration occurs at a third rate 1114. The third rate 1114 is greater than the second rate 1110 and may be the same as the first rate 1106 (e.g., as shown in FIG. 11) or different from the first rate 1106. The at least one stimulation parameter increases according to the third rate 1114 until, e.g., a titration hold is reached or the stimulation is fully titrated.

In some embodiments, the first rate 1106, second rate 1110, and third rate 1114 may be continuous rates, as shown in FIG. 11. In other embodiments, the first rate 1106, second rate 1110, and third rate 1114 may be step functions (e.g., with steps corresponding to small stimulation intensity increases that occur several times each day, such as four times a day). In such embodiments, the first rate 1106 and third rate 1114 may be greater than the second rate 1110 because, e.g., the first rate 1106 and third rate 1114 include greater stimulation parameter increases in each step and/or include steps that last for shorter periods of time compared to the steps of the second rate 1110. Additionally, in certain embodiments, the second rate 1110 may instead be a prolonged hold on the titration such that the at least one stimulation parameter is kept constant for a certain period of time (e.g., 1-7 days), after which the titration resumes at the third rate 1114. Moreover, in certain embodiments, the second rate may depend on the aggressiveness of a titration profile used to accomplish titration of the neurostimulation, the profile determined either by the physician or as determined by the VNS system 11 itself.

Performing titration according to the graph 1100 may be beneficial for patients because it has been observed that a patient's adaptation to titration is non-linear. Specifically, there is a period in the stimulation intensity progression (e.g., at a stimulation amplitude of 0.75 to 1.0 mA) where the patient's adaptation tends to stall and the patient requires additional time for adaptation to occur. Accordingly, incorporating the “dwell point” via the lowered second rate 1110 during this period (e.g., between the stimulation amplitudes of 0.75 to 1.0 mA, where 0.75 mA is the first target value 1108 and 1.0 mA is the second target value 1112) allows a patient to more smoothly adapt to the stimulation intensity while minimizing deleterious side effects.

In various embodiments, the VNS system 11 implements titration incorporating a dwell point automatically. In other embodiments, however, the VNS system 11 may incorporate a dwell period based on external input (e.g., from a physician using the programmer 40). For example, a physician may program the VNS system 11 to titrate according to the second rate for a certain number of days, until a certain stimulation amplitude is reached, and so on.

FIG. 12 is a flowchart of a titration process 1200 (e.g., implemented by the VNS system 11) that incorporates a titration dwell point, according to an exemplary embodiment. First, the VNS system 11 delivers a first neurostimulation signal with a first set of parameters at 1202. The first set of parameters has a first value for, e.g., at least one of an output current, frequency, pulse width, or duty cycle. The VNS system 11 then increases at least one of the first parameters at a first rate (e.g., the first rate 1106) until the at least one parameter reaches a first target value (e.g., the first target value 1108) at 1204. Once the first target value is reached, the VNS system 11 ceases delivery of the first neurostimulation signal at 1206.

Subsequently, the VNS system 11 delivers a second neurostimulation signal with a second set of parameters at 1208. The second set of parameters has a second value for, e.g., at least one of output current, frequency, pulse width, or duty cycle, where the second value is equal to the first target value. For the purposes of this disclosure, a first value may be considered “equal” to a second value if the first value is exactly equal to the second value or if the first and second values are within a threshold of each other (e.g., five percent). The VNS system 11 increases at least one of the second parameters at a second rate different from the first rate (e.g., the second rate 1110) until the at least one parameter reaches a second target value (e.g., the second target value 1112) at 1210. For example, as discussed above, the second rate may be less than the first rate, or the second rate may be an application of a substantially constant neurostimulation signal for a period of time. As another example, as also discussed above, the first and second rates may be stepwise functions, where the second steps are applied for greater periods of time than the first steps.

Further, as shown in FIG. 11, once the second target value is reached, the VNS system 11 may cease delivery of the second neurostimulation signal and apply a third neurostimulation signal with a third set of parameters having a third value equal to the second target value. The VNS system 11 may then increase at least one of the third parameters at a third rate that is equal to the first rate or, alternatively, different from the first rate and the second rate. In some embodiments, the VNS system 11 may also implement a hold between ceasing delivery of the second neurostimulation signal and applying the third neurostimulation signal.

As another example of titration adapted to reduce adverse side effects, FIG. 13 is a patient titration graph 1300 illustrating different titration aggressiveness profiles, according to an exemplary embodiment. The graph 1300 includes an x-axis 1302 and a y-axis 1304. The x-axis 1302 is a unit of time (e.g., days, weeks, months, etc.), while the y-axis 1304 is a parameter of stimulation (e.g., amplitude, frequency, duty cycle, etc.). In various embodiments, the titration graph 1300 may be incorporated in a user interface displayed to a physician (e.g., on the external programmer 40 or other computing device) during the titration configuration process. The aggressiveness profiles shown in graph 1300 are a medium aggressiveness profile 1306, a high aggressiveness profile 1308, and a low aggressiveness profile 1310. Each of the aggressiveness profiles 1306, 1308, and 1310 is associated with a rate of titration (e.g., an increment value between initial stimulation parameters and a target value 1312), where the rate of titration for the high aggressiveness profile 1308 is greater than the rate of titration for the medium aggressiveness profile 1306, which in turn is greater than the rate of titration for the low aggressiveness profile 1310. Accordingly, patients using the high aggressiveness profile 1308 transition to a target value 1312 from initial stimulation parameters for within a shortest time interval (e.g., 30 days), while patients using the low aggressiveness profile 1310 transition to the target value 1312 from initial stimulation parameters within a longest time interval (e.g., 60 days), and patients using the medium aggressiveness profile 1306 transition to the target value 1312 from initial stimulation parameters within an interval sometime in between the high aggressiveness profile 1308 and the low aggressiveness profile 1310 (e.g., 45 days). Alternatively, or additionally, the low aggressiveness profile 1310, the medium aggressiveness profile 1306, and the high aggressiveness profile 1308 may be associated with increasingly greater target intensity values.

With each profile 1306, 1308, and 1310, at least one stimulation parameter (e.g., stimulation current amplitude, pulse width, frequency, duty cycle, etc.) is increased (e.g., gradually increased) according to the rate of titration of the profile 1306, 1308, or 1310. In some embodiments, the rate of titration may be linear and continuous for each of the aggressiveness profiles 1306, 1308, and 1310, as shown in FIG. 13. In other embodiments, each rate of titration may instead be implemented as a step function where, e.g., the high aggressiveness profile 1308 includes steps that are the closest together in time and the low aggressiveness profile 1310 includes steps that are the furthest apart in time. For example, the titration may occur according to a fixed time interval during the daytime hours, where the number of steps implemented during that fixed time interval depends on which profile 1306, 1308, or 1310 is used.

The profiles 1306, 1308, and 1310 may also be linear, or the profiles 1306, 1308, and 1310 may be non-linear (e.g., incorporating a dwell period, as shown in FIG. 11 above, or steeper after the stimulation amplitude exceeds a threshold after which intolerance is less likely, such as 2.0 mA). Additionally, in certain embodiments, the shape, step frequency, step sizes, etc. of the profiles 1306, 1308, and 1310 may depend on which stimulation parameter is being increased according to the profile. For example, for the medium aggressiveness profile 1306 where a final stimulation with a current amplitude of 3.5 mA, a frequency of 20 Hz, and a pulse width of 500 μs is desired, the profile 1306 may include steps of 0.125 mA increments for current amplitude, 0.2 Hz for frequency, and 30 μs for pulse width. If the profiles 1306, 1308, and 1310 are step functions, at each step the increase amount and type of the stimulation increase is determined by the trajectory of the profile 1306, 1308, and 1310. As an example, at each step, amplitude, pulse width, and frequency may all increase, only one or two parameters may increase, or none of the parameters may increase depending on the trajectory of the profile 1306, 1308, and 1310 according to which the stimulation is being delivered. Together, the steps for each of the stimulation parameters create a titration curve with a smooth increase in intensity.

In various embodiments, the profiles 1306, 1308, and 1310 have the same shape and only differ on the scale of the titration. For example, the profiles 1306, 1308, and 1310 are each stepwise functions using the same sizes of steps. The profiles 1306, 1308, and 1310 instead differ based on how much time is allowed to pass between moving to the next step. Accordingly, the steps of the high aggressiveness profile 1308 are closer together (e.g. more compressed) than the medium aggressiveness profile 1306, which in turn has steps that are closer together than the low aggressiveness profile 1310. However, in other embodiments, the profiles 1306, 1308, and 1310 may instead have differently sized and/or spaced steps, the profiles 1306, 1308, and 1310 may have different shapes, and so on. Additionally, in certain embodiments, the profiles 1306, 1308, and 1310 may implement the same titration for a certain period of time (e.g., a standardized portion of the titration) and then branch out into their different, respective titration aggressiveness functions, for example, after a certain stimulation intensity threshold is reached.

For VNS systems 11 implementing different titration aggressiveness profiles, such as shown in graph 1300, the physician inputs the final stimulation parameters that the titration is designed to reach, and the default titration profile for reaching those parameters is the medium aggressiveness profile 1306. The medium aggressiveness profile 1306 may be the factory-adjustable default for the VNS system 11, or the medium aggressiveness profile 1306 may be the recommended profile for the physician to select (e.g, via the programmer 40) for the titration. The physician may then be able to customize the stimulation for the patient. For example, the physician may modify the duty cycle from the default (e.g., 14 seconds ON, 66 seconds OFF, with an amplitude ramp up at the beginning of each cycle and an amplitude ramp down at the end of each cycle), after which the duty cycle will be constant during the titration unless modified again by the physician.

Once the VNS system 11 is thus initialized, stimulation will occur according to the medium aggressiveness profile 1306. However, if the patient experiences unwanted side effects as the titration progresses, the patient can provide a feedback signal indicating that the patient is experiencing unwanted side effects to the VNS system 11, for example, via the patient magnet 730. Those of skill in the art will appreciate, however, that while reference is made herein to the patient magnet 730, the patient may be able to signal unwanted side effects to the VNS system 11 through another mechanism, such as by an external patient programmer. Once the patient signals to the VNS system 11 that the patient is experiencing unwanted side effects, the VNS system 11 modifies the titration accordingly. The VNS system 11 may also transmit, via an implantable pulse generator (e.g., the neurostimulator 12), a receipt of the feedback signal to an external device.

In one embodiment, if the patient places the patient magnet 730 over the implanted system 700 for at least 10 seconds but less than 60 seconds, the implanted system 700 automatically decrements the stimulation intensity along the profile 1306, 1308, or 1310 being used for the patient. If the titration is decremented three times, the implanted system 700 automatically switches the patient to a less aggressive titration profile, if possible. For example, the implanted system 700 switches the patient from the high aggressiveness profile 1308 to the medium aggressiveness profile 1306 or switches the patient from the medium aggressiveness profile 1306 to the low aggressiveness profile 1310. In switching to a less aggressive titration profile, the implanted system 700 identifies and moves to a location on the less aggressive titration profile that has a stimulation intensity less than or equal to the stimulation intensity currently being used on the current profile. As an example, the implanted system 700 moves to the highest location on the less aggressive titration profile that has a amplitude, frequency, and pulse width less than or equal to the amplitude, frequency, and pulse width currently being applied to the patient according to the more aggressive titration profile. Alternatively, if the patient places the patient magnet 730 over the implanted system 700 for at least 60 seconds, the implanted system 700 inhibits stimulation until the patient magnet 730 is removed. Once the patient magnet 730 is removed, stimulation resumes, and the stimulation intensity is not decremented. In some arrangements, if the patient uses the patient magnet 730 to decrement the stimulation intensity, move to a less aggressive profile, and/or pause the stimulation, the implanted system 700 keeps a record of the magnet activation. Additionally, the dashboard 800 may factor the magnet activation record into the determination of patient priority 810.

Alternatively, in another embodiment, the patient informs the physician that the patient has experienced unwanted side effects, and the physician can switch the patient to a less aggressive titration profile in response to the patient feedback. Alternatively, if the patient is experiencing no side effects, the physician can switch the patient to a more aggressive profile (e.g., from the low aggressiveness profile 1310 to the medium aggressiveness profile 1306 or from the medium aggressiveness profile 1306 to the high aggressiveness profile 1308). The physician may be able to switch the profiles in person and/or remotely.

In some arrangements, once the patient is switched from a higher aggressiveness profile to a lower aggressiveness profile, the patient cannot be switched back to the higher aggressiveness profile. Conversely, in other arrangements, the patient may be switched back to a higher aggressiveness profile (e.g., either automatically by the VNS system 11 or by the physician using the programmer 40) if the patient experiences no further subsequent side effects. Additionally, in various embodiments, the VNS system 11 keeps a record of the timing of all stimulation parameter changes throughout the titration period. The log includes a record of, e.g., the timing and duration of all magnet 730 activations and can be downloaded from the implanted system 700 for viewing by the physician.

Additionally, those of skill in the art will appreciate that graph 1300 is merely exemplary of different aggressiveness profiles. A VNS system 11 may implement additional or fewer aggressiveness profiles. For example, a VNS system 11 may be adapted to implement a titration aggressiveness profile that is even less aggressive than the low aggressiveness profile 1310. Thus, after being moved from the medium aggressiveness profile 1306 to the low aggressiveness profile 1310, a patient may indicate to the VNS system 11 (e.g., via the patient magnet 730) that the patient is still experiencing adverse side effects with the low aggressiveness profile 1310. Accordingly, the VNS system 11 may modify the neurostimulation signal to conform to the even less aggressive titration profile, deliver the modified neurostimulation signal, and titrate (e.g., gradually increase) the neurostimulation according to the even less aggressive titration profile.

FIG. 14 is a flowchart of a titration process 1400 (e.g., implemented by the VNS system 11) including different titration aggressiveness profiles, according to an exemplary embodiment. First, the VNS system 11 delivers a neurostimulation signal in conformance with a first titration aggressiveness profile at 1402. For example, the first titration aggressiveness profile may be the medium aggressiveness profile 1306 shown in FIG. 13. Next, the VNS system 11 increases at least one parameter of the first titration aggressiveness profile (e.g., output current, frequency, pulse width, or duty cycle) towards a target value (e.g., the target value 1312) at 1404. The VNS system 11 then receives a feedback signal from the patient indicating adverse effects from the neurostimulation signal at 1406. The patient may provide the feedback signal to the VNS system 11 via a patient magnet, as described above, or through any other feedback mechanism, such as by an external patient programmer. In response to the feedback signal, the VNS system 11 modifies the neurostimulation signal to conform with a second titration aggressiveness profile at 1408. For example, as discussed above, the VNS system 11 may modify the neurostimulation signal to match the low aggressiveness profile 1310 shown in FIG. 13. The VNS system 11 delivers the neurostimulation signal with the second titration aggressiveness profile at 1410. The VNS system 11 then increases at least one parameter of the second titration aggressiveness profile towards the target value at 1412.

As described above, stimulation may be applied by the VNS system 11 according to a duty cycle, where the duty cycle includes an ON period, an OFF period, an amplitude ramp up at the beginning of each cycle, and an amplitude ramp down at the end of each cycle. Accordingly, in many situations, it would be beneficial for the physician in a clinic setting to be able to determine when therapy is actually being applied by the VNS system 11. As such, referring back to FIG. 3, in addition to allowing the physician to interrogate the neurostimulator 12 and set parameters, the external programmer 40 may display indicate to the user whether the VNS system 11 is currently delivering therapy to the patient (e.g., the “therapy active” status) based on interrogation of the neurostimulator 12. In various embodiments, the external programmer 40 may display the therapy active status on the visual display 44 of the programming computer 41. For example, in one embodiment, the visual display 44 may include an on-off therapy status indicator and show via the indicator whether the neurostimulator 12 is ON or OFF. In another embodiment, in response to an interrogation of the neurostimulator 12, the external programmer 40 may display a countdown time to the next stimulation burst.

The external programmer 40 may display the therapy active status in real time. Alternatively, the external programmer 40 may display the therapy active status asynchronously from the interrogation response from the neurostimulator 12 such that the external programmer 40 accounts for the transport delay between the external programmer 40 and the neurostimulator 12 and the display of the therapy active status coincides with the stimulation burst being applied to the patient. In another arrangement, when interrogating the neurostimulator 12, the external programmer 40 may query the neurostimulator 12 to receive a block of timing data that enables the programmer 40 to sync its therapy active displays to the stimulation delivered by the VNS system 11. Additionally, in yet another arrangement, the external programmer 40 may display the therapy active status in real time or accounting for the transport delay while in communication with the neurostimulator 12 and also receive a block of timing data that enables the programmer 40 to continue displaying the therapy active status once communication ceases between the external programmer 40 and the neurostimulator 12.

FIG. 15 is a flowchart of a process 1500 (e.g., implemented by the programmer 40) of displaying an indication of active neurostimulation, according to an exemplary embodiment. The external programmer 40 first communicates with an implantable pulse generator (e.g., the neurostimulator 12) to collect data about ongoing neurostimulation applied by the neurostimulator 12 at 1502. For example, as discussed above, the external programmer 40 interrogates the neurostimulator 12 and receives back information on whether the neurostimulator 12 is currently providing active stimulation, information relating to the timing to the next active stimulation, information relating to the timing of future stimulation bursts, and so on. The external programmer 40 then displays (e.g., via the visual display 44) an indication relating to a timing of neurostimulation bursts applied by the neurostimulator 12 at 1504. As an example, the external programmer 40 may display a therapy active status such as an on-off therapy status indicator, a countdown time to the next stimulation burst, and so on. Additionally, the external programmer 40 may display the therapy active status in real time, based on a transport delay between the external programmer 40 and the neurostimulator 12 such that the display coincides with the stimulation burst actually being applied, based on a block of timing data from the neurostimulator 12, and so on.

As yet another example of titration configured to reduce adverse side effects in the patient, FIG. 16 is a patient titration graph 1600 incorporating a titration black-out period, according to an exemplary embodiment. The graph 1600 includes an x-axis 1602 and a y-axis 1604. The x-axis 1602 is a unit of time (e.g., days, weeks, months, etc.), while the y-axis 1604 is a parameter of stimulation (e.g., amplitude, frequency, pulse width, duty cycle, etc.). In various embodiments, the titration graph 1600 may be incorporated in a user interface displayed to a physician (e.g., on the external programmer 40 or other computing device) during the titration configuration process.

As shown in the graph 1600, titration may be accomplished as a step function (e.g., with multiple small stimulation intensity increase steps implemented per day, such as four times a day) incorporating one or more black-out periods 1606, shown in graph 1600 as the hold period between a start hold time 1608 and a stop hold time 1610. During the black-out period 1606, stimulation is kept constant, and no titration steps occur. Black-out periods 1606 may be implemented on titration to help ensure that the patient does not observe adverse side effects and thereby experience discomfort during the titration. For example, black-out periods 1606 may be implemented during a time of day or a duration of time during which the patient is more likely to experience side effects of the titration. Accordingly, in some embodiments, black-out periods 1606 may be implemented during the night because the increased stimulation intensity as a result of increased titration steps causes the patient to awaken. Conversely, in other embodiments, black-out periods 1606 may be implemented during the daytime, as the patient is less likely to notice an adverse side effect from the titration when the patient is sleeping.

Black-out periods 1606 may be programmed into a patient's titration schedule through various methods. In one embodiment, the timing and duration of black-out periods 1606 are preset as part of the firmware design (e.g., programmed to occur from 10 pm to 8 am, during when most individuals sleep). In another embodiment, the timing and duration of black-out periods 1606 are programmable by technicians for the VNS system 11. In a third embodiment, a physician can program a preset timing and duration of black-out periods 1606 (e.g., by using the programmer 40) based on the patient's schedule (e.g., program black-out periods 1606 during time periods when the patient is usually awake or usually asleep). In a fourth embodiment, the patient can program a preset timing and duration of black-out periods 1606 (e.g., by using the external programmer 707). In a fifth embodiment, the patient can use a user device (e.g., a handheld unit, the patient magnet 730, etc.) to indicate to the VNS device 11 when the patient is going to bed and when the patient has woken up, and the VNS device begins or suspends black-out periods 1606 accordingly. Alternatively, the patient can use the user device to delay a default black-out period 1606 or start a default black-out period 1606 early.

FIG. 17 is a flowchart of a titration process 1700 (e.g., implemented by the VNS system 11) incorporating a titration black-out period (e.g., the black-out period 1606), according to an exemplary embodiment. The VNS system 11 first delivers a neurostimulation signal at 1702. The neurostimulation signal is delivered in conformance with a set of parameters (e.g., output current, frequency, pulse width, duty cycle, etc.). The VNS system 11 begins titrating the neurostimulation signal at 1704. For example, the VNS system 11 increases (e.g., gradually increases) at least one stimulation parameter of the neurostimulation signal according to a stepwise function. The VNS system 11 then receives a first indicator associated with a titration hold time and/or a titration hold duration (e.g., the start hold 1606 instruction shown in FIG. 16) at 1706. As discussed above, the first indicator may be a preset black-out start hold time 1608 (e.g., fixed as part of the firmware design or programmed by a technician, a physician, or the patient) or may be an indicator sent by a user device to the VNS system 11 (e.g., indicating that the patient is planning on going to bed or that the patient has awoken).

In response, the VNS system 11 holds titration of the neurostimulation signal by continuing the neurostimulation signal at the signal parameters being delivered at the time the first indicator was received at 1708. Subsequently, the VNS system 11 receives a second indicator associated with a titration resumption time and/or the completion of the titration hold time (e.g., the stop hold time 1610) at 1710. For example, as discussed above, the second indicator may be the expiration of the preprogrammed black-out period or may be an indicator sent by the user device to the VNS system 11 (e.g., indicating that the patient has awoken or that the patient is planning on going to bed). In response to the second indicator, the VNS system 11 resumes titrating the neurostimulation signal at 1712. Additionally, while FIG. 16 illustrates a resumption of the titration after the black-out period 1606 occurring at the same level as before the black-out period 1606, in some embodiments, the VNS system 11 may increase the neurostimulation after the black-out period 1606 and/or modify the rate of the titration after the black-out period 1606. As such, through the titration process 1700, a temporary titration hold may be applied to the neurostimulation provided to the patient to reduce adverse effects observed by the patient during the titrating.

In various embodiments, the VNS system 11 may also be configured to provide “titration training” to the patient under the supervision of a physician. The goal of the titration training is to provide increasing stimulation intensity to the patient at a controlled rate over a relatively short period of time (e.g., 10 minutes) so that the patient can experience the sensation of stimulation. For example, at the beginning of the titration period for a patient, the physician interacts with the patient in a titration training session. During the session, the VNS system 11 provides stimulation levels that are (1) imperceptible, (2) perceptible but tolerable, and/or (3) perceptible and slightly intolerable to the patient (e.g., in response to an indication from the physician via the external programmer 40 to conduct titration training). By educating the patient, and well as the patient's caregiver in certain arrangements, through the titration training session on the expected levels of stimulation during the titration period, patients may become acclimated to the sensation of mild stimulation in the midst of rapid accommodation to stimulation. In this way, the training may improve the timeliness and sensitivity of magnet interventions from the patient in response to the titration (e.g., by teaching the patient what side effects feel like so that the patient only uses the magnet interventions when a side effect is actually present). As such, these training sessions may help the titration and patient accommodation processes to proceed smoothly without unnecessary interruptions. These sessions may also allow the physician to assess the patient and/or caregiver motivation, cognitive ability, and physical abilities before the physician activates the titration.

While embodiments been particularly shown and described, those skilled in the art will understand that the foregoing and other changes in form and detail may be made therein without departing from the spirit and scope. For example, in various embodiments described above, the stimulation is applied to the vagus nerve. Alternatively, spinal cord stimulation (SCS) may be used in place of or in addition to vagus nerve stimulation for the above-described therapies. SCS may utilize stimulating electrodes implanted in the epidural space, an electrical pulse generator implanted in the lower abdominal area or gluteal region, and conducting wires coupling the stimulating electrodes to the generator.

The present disclosure contemplates methods, systems, and program products on any machine-readable media for accomplishing various operations. The embodiments of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

Although the figures may show a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.

Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, Z, X and Y, X and Z, Y and Z, or X, Y, and Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. 

What is claimed is:
 1. A neurostimulation system comprising: an implantable medical device (IMD) comprising a neurostimulator coupled to an electrode assembly, the neurostimulator comprising: an implantable pulse generator configured to generate a neurostimulation signal delivered to a patient via the electrode assembly; and a control system programmed to: deliver the neurostimulation signal in conformance with a first titration aggressiveness profile, the first titration aggressiveness profile having a first set of parameters having one or more first values for one or more of output current, frequency, pulse width, or duty cycle of the neurostimulation signal; increase the one or more of output current, frequency, pulse width, or duty cycle from the one or more first values towards one or more target values; receive a feedback signal from the patient indicating an adverse effect from the neurostimulation signal; and in response to the feedback signal: modify the neurostimulation signal to conform with a second titration aggressiveness profile, the second titration aggressiveness profile having a second set of parameters having one or more second values for the one or more of output current, frequency, pulse width, or duty cycle; deliver the neurostimulation signal with the second titration aggressiveness profile; and increase the one or more of output current, frequency, pulse width, or duty cycle from the one or more second values towards the one or more target values; wherein the second titration aggressiveness profile corresponds to a less aggressive titration and the first titration aggressiveness profile corresponds to a more aggressive titration, the more aggressive titration defined by at least one of the following as compared to the less aggressive titration: a shorter time interval associated with a transition from the first set of parameters to one or more target values, a greater target intensity, or greater increment values between the one or more first values and the one or more target values.
 2. The neurostimulation system of claim 1, wherein the control system is further programmed to: receive a second feedback signal from the patient indicating an adverse effect from the neurostimulation signal; modify the neurostimulation signal to conform with a third titration aggressiveness profile, the third aggressiveness profile having a third set of parameters having one or more third values for the one or more of output current, frequency, pulse width, or duty cycle; deliver the neurostimulation signal with the third titration aggressiveness profile; and increase the at least one of output current, frequency, pulse width, or duty cycle from the one or more third values towards the one or more target values.
 3. The neurostimulation system of claim 2, wherein the third titration aggressiveness profile corresponds to a least aggressive titration, the less aggressive titration of the second titration aggressiveness profile defined by at least one of the following as compared to the least aggressive titration of the third titration aggressiveness profile: a shorter time interval associated with a transition from the first set of parameters to the target value, a greater target intensity, or greater increment values between the first value and the target value.
 4. The neurostimulation system of claim 1, wherein the control system is programmed to modify the neurostimulation signal after receiving the feedback signal a plurality of times.
 5. The neurostimulation system of claim 1, wherein the neurostimulator further comprises a magnet detection circuit configured to detect a presence of a magnet in proximity of the implantable pulse generator; and wherein the control system is configured to receive the feedback signal by detecting the feedback signal using the magnet detection circuit.
 6. The neurostimulation system of claim 1, wherein the control circuit is further programmed to transmit, via the implantable pulse generator, receipt of the feedback signal to an external device.
 7. The neurostimulation system of claim 1, wherein the control system is further programmed to: increase the one or more of output current, frequency, pulse width, or duty cycle from the one or more second values towards the one or more target values at a first rate until the one or more of output current, frequency, pulse width, or duty cycle reaches one or more intermediate target values; and subsequently increase the one or more of output current, frequency, pulse width, or duty cycle from the one or more intermediate target values towards the one or more target values at a second rate.
 8. The neurostimulation system of claim 7, wherein the second rate is lower than the first rate.
 9. The neurostimulation system of claim 7, wherein the one or more intermediate target values are one or more first intermediate target values, and wherein the control system is further programmed to: increase the one or more of output current, frequency, pulse width, or duty cycle from the one or more first intermediate target values towards the one or more target values at a second rate until the one or more of output current, frequency, pulse width, or duty cycle reach one or more second intermediate target values; and subsequently increase the one or more of output current, frequency, pulse width, or duty cycle from the one or more second intermediate target values towards the one or more target values at a third rate.
 10. The neurostimulation system of claim 9, wherein the third rate is equal to the first rate.
 11. A method of titrating a neurostimulation signal delivered to a patient from an implantable pulse generator, the method comprising: delivering the neurostimulation signal in conformance with a first titration aggressiveness profile, the first titration aggressiveness profile having a first set of parameters having one or more first values for one or more of output current, frequency, pulse width, or duty cycle of the neurostimulation signal; increasing the one or more of output current, frequency, pulse width, or duty cycle from the one or more first values towards one or more target values; receiving a feedback signal from the patient indicating an adverse effect from the neurostimulation signal; and in response to receiving the feedback signal: modifying the neurostimulation signal to conform with a second titration aggressiveness profile, the second titration aggressiveness profile having a second set of parameters having one or more second values for the one or more of output current, frequency, pulse width, or duty cycle; delivering the neurostimulation signal with the second titration aggressiveness profile; and increasing the one or more of output current, frequency, pulse width, or duty cycle from the one or more second values towards the one or more target values; wherein the second titration aggressiveness profile corresponds to a less aggressive titration and the first titration aggressiveness profile corresponds to a more aggressive titration, the more aggressive titration defined by at least one of the following as compared to the less aggressive titration: a shorter time interval associated with a transition from the first set of parameters to the one or more target values, a greater target intensity, or greater increment values between the one or more first values and the one or more target values.
 12. The method of claim 11, further comprising: receiving a second feedback signal from the patient indicating an adverse effect from the neurostimulation signal; modifying the neurostimulation signal to conform with a third titration aggressiveness profile, the third titration aggressiveness profile having a third set of parameters having one or more third values for the one or more of output current, frequency, pulse width, or duty cycle; delivering the neurostimulation signal with the third titration aggressiveness profile; and increasing the one or more of output current, frequency, pulse width, or duty cycle from the one or more second values towards the one or more target values.
 13. The method of claim 12, wherein the third titration aggressiveness profile corresponds to a least aggressive titration, the less aggressive titration of the second titration aggressiveness profile defined by at least one of the following as compared to the least aggressive titration of the third titration aggressiveness profile: a shorter time interval associated with a transition from the first set of parameters to the target value, a greater target intensity, or greater increment values between the first value and the target value.
 14. The method of claim 11, wherein modifying the neurostimulation signal occurs after receiving the feedback signal a plurality of times.
 15. The method of claim 11, wherein receiving the feedback signal comprises detecting the feedback signal using a magnet detection circuit configured to detect a presence of a magnet in proximity of the implantable pulse generator.
 16. The method of claim 11, wherein increasing the one or more of output current, frequency, pulse width, or duty cycle from the one or more second values comprises increasing the one or more of output current, frequency, pulse width, or duty cycle from the one or more second values towards the one or more target values at a first rate; and wherein the method further comprises subsequently increasing the one or more of output current, frequency, pulse width, or duty cycle from the one or more intermediate target values towards the one or more target values at a second rate.
 17. The method of claim 16, wherein the second rate is lower than the first rate.
 18. A non-transitory computer-readable medium storing instructions executable by a processor to: deliver a neurostimulation signal in conformance with a first titration aggressiveness profile, the first titration aggressiveness profile having a first set of parameters having one or more first values for one or more of output current, frequency, pulse width, or duty cycle of the neurostimulation signal; increase the one or more of output current, frequency, pulse width, or duty cycle from the one or more first values towards one or more target values; receive a feedback signal from the patient indicating an adverse effect from the neurostimulation signal; and in response to the feedback signal: modify the neurostimulation signal to conform with a second titration aggressiveness profile, the second aggressiveness profile having a second set of parameters having one or more second values for the one or more of output current, frequency, pulse width, or duty cycle; deliver the neurostimulation signal with the second titration aggressiveness profile; and increase the one or more of output current, frequency, pulse width, or duty cycle from the one or more second values towards the one or more target values; wherein the second titration aggressiveness profile corresponds to a less aggressive titration and the first titration aggressiveness profile corresponds to a more aggressive titration, the more aggressive titration defined by at least one of the following as compared to the less aggressive titration: a shorter time interval associated with a transition from the first set of parameters to the one or more target values, a greater target intensity, or greater increment values between the one or more first values and the one or more target values.
 19. The non-transitory computer-readable medium of claim 18, wherein the instructions are further executable to: receive a second feedback signal from the patient indicating an adverse effect from the neurostimulation signal; modify the neurostimulation signal to conform with a third titration aggressiveness profile, the third titration aggressiveness profile having a third set of parameters having one or more third values for the one or more of output current, frequency, pulse width, or duty cycle; deliver the neurostimulation signal with the third titration aggressiveness profile; and increase the at least one of output current, frequency, pulse width, or duty cycle from the one or more third values towards the one or more target values.
 20. The non-transitory computer-readable medium of claim 18, wherein the instructions are executable to modify the neurostimulation signal after receiving the feedback signal a plurality of times. 